Last April, the Supreme Court declared another campaign finance regulation unconstitutional. In McCutcheon v. FEC, a five-justice majority determined that Congress could not limit the aggregate amount an individual can give directly to federal candidates, political action committees, and party committees. For four decades, campaign finance law had placed caps on aggregate individual donations (in 2012, those caps were $70,800 to parties and committees, $46,200 to candidates, and $117,000 combined, limits that have been adjusted for inflation over the years). Shaun McCutcheon, the plaintiff, argued that these limits violated his constitutional rights. Chief Justice John Roberts, writing for the majority, agreed, arguing, “The right to participate in democracy through political contributions is protected by the First Amendment…. ” For now, limits on how much individuals can give directly to a single candidate ($5,200 per two-year cycle) still stand. But they may be just one court challenge away.

The logic of McCutcheon followed closely on the logic of Citizens United, which famously paved the way for outside organizations to spend unlimited sums of money on elections. The logic is this: Congress may regulate campaign finance only to “protect against corruption or the appearance of corruption.” Any other rationale is unjustifiable.

But what counts as “corruption”? Read more closely into the McCutcheon decision and you soon find that only one type of corruption can ever justify limits on the supposedly sacrosanct freedom of speech manifested in the writing of multimillion-dollar checks to help out favored candidates. That type of corruption is “quid pro quo” corruption. Here is the key passage in the McCutcheon decision:

[W]hile preventing corruption or its appearance is a legitimate objective, Congress may target only a specific type of corruption—“quid pro quo” corruption…. Spending large sums of money in connection with elections, but not in connection with an effort to control the exercise of an officeholder’s official duties, does not give rise to such quid pro quo corruption. Nor does the possibility that an individual who spends large sums may garner “influence over or access to” elected officials or political parties.

Notice what has happened here. The Court has said that the only thing that legitimizes regulating campaign finance is a very narrow, almost impossibly difficult-to-prove manifestation of corruption—the naked and bold trading of political favors for money. But by all indications, this kind of blatant bribery is a rare occurrence in Washington. Politicians and lobbyists are simply too careful to risk the career-ending scandal that arises from crude “House of Cards”-style skullduggery.

After all, there are so many legitimate ways to get ahead in Washington. The nation’s capital may be awash in money. That money may buy special access. It may consistently tilt politics in the direction of the rich. It may alter the types of people who run for office in the first place and how they spend their days and whom they listen to. But to the conservatives on the Supreme Court, well, that’s just politics. If government is most responsive to those constituents who participate most actively, or give the most money, so be it. For the Roberts Court, responsiveness is simply part of democracy.

Zephyr Teachout has a different view. Teachout, a law professor at Fordham University who challenged Andrew Cuomo in the New York State Democratic gubernatorial primary this fall (and lost, but hit a respectable 34 percent), has written an intelligent, stimulating, and wide-ranging retort to the Roberts Court’s constrained view of corruption. In Corruption in America, she argues that for democracy to thrive, we need a far more capacious characterization of this key concept. Rather than wait for prosecutors to find the $90,000 in cold, hard cash in the congressman’s freezer in exchange for promoting a company’s business interests—as happened with Rep. William Jefferson, Democrat of Louisiana—Teachout wants to prevent the congressman from being tempted to take the money to do the favor in the first place. For Teachout, corruption is a much more existential threat to effective democracy, and one that requires active attention. Sure, she argues, some public officials might have the moral fortitude to stand up to their largest campaign contributors. But why have them rely on private contributions in the first place? Shouldn’t we do everything in our power to encourage our government to think more about public, rather than private, interests?

Teachout devotes considerable effort to proving that she is the true originalist here. In her telling, the Founding Fathers were obsessed with corruption. They saw it as a ubiquitous threat to democracy. Steeped in Aristotle, Montesquieu, Locke, Edward Gibbon, and the Christian Bible, the Founders viewed corruption as not merely transactional (Roberts’s concept of quid pro quo). They considered it a form of moral decay. Corruption meant a falling away from the civic virtues on which the Founders hoped to build a nation. Madison repeated the word corruption 54 times in his notebook from the summer of 1787. Teachout notes, “The question that haunted the convention was this: would these men manage to wrangle the worst impulses of rulers and ruled and transform them into representatives and citizens? If so, for how long?”

Answering this question has been a legal work in progress ever since. Throughout American history, lawmakers and courts have struggled with the definitions and boundaries of corruption. Teachout recounts many of these struggles, making her book in part a greatest hits of court cases and laws dealing with bribery and lobbying, full of corrupt land deals and railroad intrigue.

The obvious challenge is that there are few bright lines. On the question of lobbying, for example, how does one “distinguish between illegitimate sale of private influence and legitimate, lawyer-like behavior”? How does one prove corrupt intent? Sometimes courts and legislatures allow private interests to triumph; other times they guard the public interest tightly. But the key point is that they do struggle. And in the history of American discourse on corruption, Teachout finds a long tradition of justices and lawmakers being very concerned about corruption and casting it far more broadly than the simple quid pro quo.

But in 1976, something changed. In Buckley v. Valeo, the Supreme Court had to decide whether the 1971 Federal Election Campaign Act, amended in 1974 to place caps on both contributions and expenditures, unfairly restricted political speech. The Court ruled that campaign spending was a form of speech, and therefore Congress couldn’t regulate expenditures. But the Court also determined that Congress did have a significant interest in preventing corruption, and since large individual contributions to candidates could be seen as corrupting, Congress was entitled to limit contributions. In this process, corruption got elevated as a key concept, as a justification for regulating campaign contributions. However, this elevation was “accompanied by a simultaneous lack of guidance on how to understand the concept. The Court used the word corruption but didn’t explain where we should look to define it, or how we should understand it.”

For a while, this lack of guidance was not disastrous for the cause of campaign finance regulation. Even through the 2003 McConnell v. FEC decision, which upheld the “soft money” ban of the Bipartisan Campaign Reform Act of 2002 (aka McCain-Feingold), the Court managed to hold a somewhat expansive definition of corruption, stating that Congress had a legitimate interest in “both the actual corruption threatened by large financial contributions and…the appearance of corruption” that could result from soft money. But in Citizens United, the Court dramatically changed course. The Court, Teachout writes, “took that which had been named corrupt for over two hundred years and renamed it legitimate and the essence of responsiveness.” For most of U.S. history, the term “quid pro quo” was rarely used in court cases. Through 1950, it appeared only ten times. Even up through 1976, it appeared fewer than 100 times. In Citizens United, it is used 14 times. “After Citizens United,” writes Teachout, “there is only one kind of thing that is clearly corrupt: openly asking for a deal in exchange for a specific government action. The vast range of inappropriate dependencies and self-serving behavior that made up the web of the world of corruption for the founders is gone.”

Teachout wants to restore the earlier view of corruption. “I am trying to bring corruption back,” she writes. “Not as a societal ill….But as an idea, something we fight and worry about. My hope is that courts and citizens will recognize that the anticorruption principle is a foundational American principle and will incorporate it into jurisprudence and public debate.” Though Teachout acknowledges the difficulties in defining “an important concept with unclear boundaries,” she takes her best shot. Corruption, she writes, “refers to excessive private interests in the public sphere; an act is corrupt when private interests trump public ones in the exercise of public power, and a person is corrupt when they use public power for their own ends, disregarding others.”

There is an obvious challenge here. To narrow corruption to the purely transactional exchange of favors for cash means confining it to something too rare to ever usefully compete with the goliath of the First Amendment. But to define it too broadly creates a different set of problems. If one sees potential corruption everywhere, it becomes difficult to govern. One must constantly set up boundaries to insulate and protect lawmakers from private pressure. But private interests have plenty of good policy ideas, too. And public servants can easily lose touch with reality and wind up concocting impractical schemes if they cut off all communication with private interests.

For guidance on how to strike a balance, Teachout turns to James Madison and Theodore Roosevelt. From Roosevelt, she gains an appreciation for what she calls “prophylactic” rules that seek to prevent the behavior from occurring in the first place. As opposed to “corrupt intent laws” (like bribery or quid pro quo rules), Teachout prefers structural boundaries on the temptations lawmakers encounter. Corrupt-intent laws are hard to enforce because intent is hard to prove. Teachout advocates public funding of elections, which would remove from lawmakers the temptation of having to do favors for campaign contributors by removing the campaign contributors. She also advocates strong anti-monopoly laws: “Corruption as understood by the framers flows from monopoly because the monopolists can extract political concessions and subsidies from their role as little autocrats of their individual markets.”

In Madison, Teachout finds the balancing act between public and private: “[O]ne should not suppress or override private interests [italics in original], but rather pursue them in congruence with the public good.” She advises channeling Madison’s delicate mix of realism and idealism, which relies on two counterpoised principles: “men are not always angels and therefore structures must help us”; “virtue is necessary, and structures alone cannot help us.” Put another way: Let’s do all we can to create a political environment in which the temptation to serve narrow private interests is limited. But let’s not think that rules alone can solve all our problems. We also need a civic culture of public-spirited vigilance. “It is valuable and possible,” Teachout writes, “to aspire to a society where those in government are concerned on a daily basis with the well-being of the public.”

But what is the “well-being of the public” of which she writes? Concepts like the “public interest” and the “public good” are central to Teachout’s arguments, yet they are repeatedly cast as self-evident. While we might easily agree that democracy should not be simply a bidding war among private interests, that is a definition by absence. In a nation of 319 million people, with impressive diversity of wealth and ethnicity and geography and occupation and values, what counts as the public good? What happens when different factions have opposing concepts of the public good? What happens when there are trade-offs between fundamental public goods like liberty and equality, freedom and security? To be fair, Teachout is not alone in positing a concept of the public interest without any clear or affirmative vision of it. This is a wide problem in the discourse around political reform, which too often takes the “public interest” to be obvious and simply moves on.

Modern political influence is in many ways a battle over how one defines the public interest. Much lobbying attempts to show that the big banks or the large pharmaceutical companies or the giant telecoms are actually aligned with the well-being of the public. When I worked in the Senate during the writing of the Dodd-Frank financial reform bill, every bank lobbyist had a story about how the banks were basically the good guys and how more regulation would have unintended consequences, or how Congress was going to kill jobs, or stymie the recovery, or some other parade of horribles that would most definitely not be in the public interest. Pharmaceutical companies trot out patients whose lives have been saved by their drugs. In the battle over net neutrality, telecom companies promise that they, too, share the hopes and dreams of a faster, open Internet. In today’s Washington, one party believes that the public good amounts to government getting out of the way while private business operates with only the lightest of regulation. There are many who honestly believe that letting the wealthiest keep more of their money is in the public interest. Is lobbying for such ideas corruption?

The obvious problem here is that not all factions have equal resources to communicate their vision of the public interest. By my calculation, business interests (individual corporations and business associations) now spend 34 times more on lobbying than do their potential countervailing forces (unions and “public interest” groups). Large companies also spend considerable resources shaping the intellectual environment through funding think tanks and academic research and symposia—that is, by shaping elite consensus. Spreading ideas is by no means quid pro quo corruption. But in a world where resources to spread ideas are highly unequal, the outcomes of such distortions can feel a bit like corruption.

Like Teachout, my preferred solutions also rely on Madison’s political philosophy. I retain a faith in the old Madisonian idea of faction counteracting faction as our best hope. But there has been a market failure in the production of advocacy, because the unequal distribution of financial resources has a way of generating an unequal distribution of political resources. If the market for ideas is to function properly, government needs to play an affirmative role. To this end, government should experiment with a public defender model for interests that are chronically underrepresented in Washington, perhaps through direct subsidies to those groups. Teachout, in these very pages, has proposed an “office of public lobbyists who, like public defenders, are responsible for representing any group of people who feel their viewpoints are not being represented in Congress.” [See “Original Intent,” Issue #11.] It’s a terrific idea. I’ve also argued that lobbying should move to a more public platform online, where everybody would have access and could more easily fact-check opponents’ arguments (rather than having to rely on private meetings).

This type of thinking puts me in the camp of what Teachout calls equality theorists (in which she includes Rick Hasen, Kathleen Sullivan, David Strauss, and my sometime co-author Bruce Cain; I’d also add Justice Stephen Breyer). Teachout is for equality, too. It’s just that she thinks corruption is a separate concern, and she is worried that equality theorists tend to see politics too mechanically, treating lawmakers as dispassionate aggregating devices, who do nothing more than tally up the various pleadings on both sides and pick the winner. As she writes, “The formal consideration of valuing each person’s interest equally is emotionally different from faithfulness and identification with the public good.”

There again is that pesky concept of the “public good.” Corruption might be a departure from the public good. But the public good isn’t some Platonic principle that can be divined through quiet contemplation. It can emerge only through the practice of politics, and it must constantly adapt to changing circumstances. Its grammar inevitably comes from the private interests that are constantly trying to privilege their values and folk theories as the highest expressions of the public interest while denigrating others’ values and folk theories as mere self-interest. That’s why equality considerations need to be part of any conversation about corruption. Without equal participation from all perspectives, the grammar of the public interest will inevitably be limited to its most well-funded suppliers. To ignore the fight over the “public good” by taking it as self-evident seems to me to miss the central battle of self-government.

While there is obviously plenty to debate and disagree over in how we might define and delineate corruption, the broad unsettledness of the concept is perhaps Teachout’s point. She has some ideas on how we might think about corruption, and she highlights others’ ideas as well. But mostly, she just wants us to debate and discuss corruption more, to view it as a controversial issue, and not to let the Roberts Court sweep it away into a marginal corner so that it can then declare it irrelevant, thus clearing the way for unlimited campaign contributions.

In the long term, we need to think hard about making it easier for more people to participate in the political process. In the short term, the current Court has ruled out my preferred arguments of equality and distortion as justifications for limiting money in politics, and instead decided that corruption is the only legitimate justification. Which means that the battle over the definition of “corruption” has potential to be a live battle. If so, Teachout’s book may be just the rousing call to arms we need for the fight ahead.