Bernie Sanders has a simple explanation of why the US hasn't achieved universal health care yet: money.

"Do you know why we can’t do what every other country — major country — on Earth is doing?" he asked during the January 17 Democratic debate. "It’s because we have a campaign finance system that is corrupt, we have Super PACs, we have the pharmaceutical industry pouring hundreds of millions of dollars into campaign contributions and lobbying, and the private insurance companies as well."

Sanders is the most vocal exponent of this critique currently, but he's hardly the only one. At least since the progressive movement of the early 1900s, a prominent strain of American liberalism has identified the undue influence of moneyed interests, primarily through campaign donations and lobbying, as the fundamental problem in American politics, the one issue that needs to be fixed before the political system is capable of fixing anything else.

Sanders's version is actually more plausible than the one others have articulated. He ties it to a broader call for working-class unity and revolution. More typical is the less comprehensive version Harvard law professor Lawrence Lessig expressed during his short-lived presidential bid, which holds that if Congress were to simply pass some good government reforms — in particular campaign finance reform — legislation that liberals have been pushing for generations would suddenly be possible, even easy, to pass.

It's a tempting notion. But some states have actually enacted public financing, and liberal utopias didn't follow. The laws had some good effects, but they did not make Sanders's personal platform dramatically easier to pass.

Two states already have a version of publicly financed elections

The most frequently proposed remedy for the influence of money in politics is a system of public financing. And advocates have had some success in passing that reform at the state level. Both Arizona and Maine have adopted "Clean Elections" systems, in which candidates have to secure a fixed number of $5 donations and then get a lump sum from the government with which to campaign. In return, they agree to not solicit more donations and to cap their spending.

The effects of these programs are ably summarized in Barnard College political scientist Michael Miller's book Subsidizing Democracy. The image Miller produces of life under public financing is really appealing. Clean Elections, he concludes, "not only eliminates the time costs of fundraising but also fosters greater interaction between candidates and voters."

"I would not be remotely comfortable saying that a Clean Elections system would move the country to the left"

With candidates no longer forced to spend hours upon hours every day raising money, they instead talk to their constituents. Miller also finds that public funding enables people who wouldn't otherwise run to become candidates, increasing the quality of the candidate pool. And it reduces "roll-off," the tendency of voters already at their precinct to just not vote in races lower down on the ballot, like state rep or county commissioner or whatever.

But Miller didn't find a huge effect on the views of the people elected. Public financing didn't make it likelier for Democrats to win. It didn't make Arizona or Maine more liberal overall. There isn't some sweeping redistributive bill Arizona passed that it couldn't have made it through before public financing.

This was confirmed by a subsequent paper Miller wrote with University of Denver political scientist (and Vox contributor) Seth Masket. "My paper with Seth finds very little evidence that accepting public funding influences extremism for either party in Arizona or Maine (this covers polarization and 'drift')," Miller told me.

"Nor is there any evidence that Clean Elections advantages Democrats in elections. Indeed, while participating candidates shrink their opponents' victory margins, there is no evidence that accepting CE subsidies swings election outcomes at all. So if you were going to lose, you'll still lose … just by less."

You can see this in the states' subsequent election results. "There has always been a huge GOP majority in the Arizona legislature, and if anything, Republicans have made gains in Maine," Miller continues. "So I would not be remotely comfortable saying that a CE-style system would move the country to the left."

Why doesn't campaign finance matter more?

This is plausible if you consider the role that campaign money actually plays in the thinking of members of Congress. Cases of outright bribery — "we'll donate to your campaign if you vote for this bill" — are pretty rare. What's more common than buying votes is buying apathy.

"When people are giving campaign contributions, what they're really buying is disinterest," Steven Teles, a political scientist at Johns Hopkins and fellow at New America, says, citing research by Richard Hall and Frank Wayman. "They're paying people to think, 'Eh, there are a million things I could pay attention to, why pay attention to that?'"

But Teles notes that Lobbying and Policy Change — a major study of how lobbying works from Frank Baumgartner, Jeffrey Berry, Marie Hojnacki, David Kimball, and Beth Leech on lobbying — suggests that this dynamic breaks down in times of "policy punctuation": when the normal slow pace of Congress is broken and the whole body's attention, and that of the public, is turned to a very high-profile issue. Think of the few months when Congress was monomaniacally focused on health care reform in late 2009 and 2010, or on immigration in 2013.

"Money only buys you disinterest when the thing's not on the agenda," Teles says. "A few thousand-dollar campaign contributions are enough to get you not to pay attention to something when nobody else is paying attention to it. But when voters are paying attention and you think there's some probability an opponent can run a campaign ad against you about this, preventing that is of way more value than a few thousand-dollar contributions."

Thomas Stratmann, an economist at George Mason who studies campaign finance, agrees. "In my view, political money is unlikely to have much impact on well publicized issues, such as gun control or single-payer issues," he writes in an email. "Money is more likely to be important for issues that are not on the radar screen of TV, newspapers, and social media, perhaps something like subsidies for sugar farmers."

It's harder to reform lobbying than you'd think

So regulating campaign finance better wouldn't turn American policymaking dramatically leftward. But would a more dramatic reform? In particular, would regulating lobbying in addition to campaign funding do more to move politics leftward? "The extent of the reform is going to greatly affect how much of a difference it would make," Clayton Peoples, a sociologist at the University of Nevada Reno, told me. "The more comprehensive the reform, the more Congress would move away from corporate interests."

I see where Peoples is coming from, but research on lobbying suggests that lobbyists are not the omnipotent power brokers that voters sometimes imagine them to be. Further, it suggests that insofar as they matter, they matter for reasons that are hard to regulate away.

The relationship between lobbying and policy outcomes is complex and not reducible to "people with more cash win." One of the big lessons of Lobbying and Policy Change, the lobbying study from Baumgartner, Berry, Hojnacki, Kimball, and Leech, is that while lobbying coalitions tend to win more often in cases where resources are hugely asymmetrical — where one side has tons of cash and institutional support and the other has very little — in cases where the sides are each well-resourced, it's hard to find much of an effect from additional money.

Perhaps more surprisingly, only 19 of the 98 policy fights analyzed by Baumgartner et al. featured a resource allocation that tilted. In more than 80 percent of cases, the sides were more evenly matched, and resources weren't a particularly good predictor of success.

That's because big fights tend to provoke a counter-mobilization. When conservative groups came together to support President George W. Bush's push for Social Security privatization in 2005, the AARP and liberal groups mobilized against them. When environmental groups came together to push for cap-and-trade legislation in 2009 and 2010, the oil and gas industries mobilized against them. The normal outcome is that the sides are roughly evenly matched and fight to a draw.

This makes sense if you think about it. If the sides were super lopsided, the dominant side should've already gotten what it wanted years ago. If things haven't happened yet, that's probably because there's a sizable constituency keeping it from happening.

This is of small comfort to lefties like Sanders who rail against the status quo and focus on overturning it. The intense status quo bias of the existing system obstructs conservative change as well, but it also serves to keep policies social democrats and liberals oppose — private health insurance, high public college tuition, low capital requirements on banks, etc. — in place. If anything, this should make Sanders's case that money in politics is the key problem more compelling.

There's more to lobbying than just money

But Baumgartner et al. also find that lobbyists don't get their power merely from cash. They gain influence by offering specialized information that legislators need but don't have, by gaining allies in the executive branch and among members of Congress, and by leveraging large grassroots organizations. And most of those levers of influence can't be regulated away.

Consider the case of gun control. Universal background checks aren't hard to pass because gun manufacturers can outspend gun control advocates. They're hard to pass because the National Rifle Association is much, much better organized and better able to mobilize members than any group favoring action on guns.

Or consider health care reform. A big part of Bernie Sanders's single-payer plan is a reduction in payments to doctors. That means it'd face opposition not just from corporate interests — PhRMA, health insurers, etc. — but from the American Medical Association and other professional groups. Even if you somehow got all corporate money out of Washington, there's no way to stop organized groups of citizens like the AMA from advocating for themselves — or at least no way that doesn't abrogate the freedom of assembly.

This is not to say that there's nothing to be done to limit lobbyists' power, particularly corporate lobbyists' power. New America's Lee Drutman (a Vox contributor) and Teles propose in a Washington Monthly essay increasing the amount of non-lobbyist expertise to which members of Congress have access. That means doubling congressional committee staff and making those positions into career civil service posts like those in the Congressional Budget Office, and improving all staffer pay to lengthen tenures and reduce the temptation to quit and join lobbying firms.

That would do a lot of good by reducing legislators' reliance on information provided by lobbyists. It would lead to more informed, less industry-captured policy. But even if the Drutman/Teles reform were to pass, defense contractors would be able to make alliances with members of Congress with big bases in their districts. Banks would still fund lawsuits challenging new regulations. Health insurers will still run Harry and Louise–style ads to build public opinion against health reform. Reformers can plug some holes, but money will find a way to influence the policy process regardless.

The basic issue is that the economy continues to grow, and with it so do incentives for businesses to lobby government for a bigger slice of the pie. "The American economy is so ginormous," Baumgartner said in a phone interview. "All that money and all those diverse interests are increasingly concentrated on the same target as in 1960. We still have 435 congressmen and 100 senators, and the GDP is much bigger. … That's absent from the literature, and there's not much you can do about it."

The structure of the American government makes passing legislation hard

The obsession with money in politics also obscures the role the structure of the American system of government plays in blocking left-wing legislation.

Due to both gerrymandering and a desire to draw "natural-looking" districts, Democrats tend to have bigger winning margins in House races than Republicans do. That means they get fewer seats than you'd expect based on their share of the popular vote, which in turn biases policy to the right.

Same goes for the US Senate, which by offering equal representation to Wyoming and California vastly amplifies the influence of tiny, rural white states, which lean Republican.

Then there's the whole Madisonian structure of the American government. To enact a law in Denmark, one simply schedules a vote in its unicameral parliament, and if the bill passes it becomes law. In the US, the House and Senate must each pass legislation, then agree on a compromise between their two versions, then pass the compromise again, and then get the president to sign it.

There are many more "veto points" in the US system, places where actors can scuttle proposed legislation. That's on purpose. "The US Constitution is designed to create stalemate," Baumgartner says. "If we wanted to point to the reasons for stalemate, we should point to the genius of the Founding Fathers before we turn to lobbying."

The real problem for the left is that many Americans are conservative, and that's never going to change

The problem is even deeper than structure, however. Embedded in the Sanders/Lessig critique is the idea that if we somehow reformed the American system of government so that it perfectly reflected the people's will, untainted by corporate influence or government structures currently stopping progress, the resulting policies would be much more left-wing.

It seems plausible that they'd be somewhat more left-wing. But the fact of the matter is that American public opinion is polarized and many Americans are conservative. Many more are self-styled moderates or liberals who are nonetheless skeptical of big changes like free college or single-payer. These policies tend to poll well when you phrase them sympathetically — say, by asking about "Medicare for all" — and poorly when you don't (say, by asking if a government-run health care system is better than a privately run one).

Even in a world in which there is no lobbying, plenty of Americans will be skeptical of the government's ability to perform crucial tasks, and will in turn elect members of Congress who will oppose expansions of government power.

"I think the resistance to programs like national health insurance reflects a deep stream in our political culture that is skeptical of the ability of government to do things well," political scientist Doug Roscoe of the University of Massachusetts Dartmouth says. "Americans have almost always favored private economic activity over public programs."

This point becomes clearer if you try to imagine how progressive legislation would get through in a world where reforms like public financing and better congressional staffing were passed. One possibility is that those reforms just mean the Democrats constantly win majorities. But Arizona and Maine's experiences suggest that's not really the case. And if it isn't, why do we think Republicans in such a world will suddenly be eager to pass welfare state expansions?

"The key question is whether Republican candidates would be supportive of [single-payer] without campaign contributions — I think the answer is no here," political scientist Shannon Jenkins at UMass Dartmouth adds. "Rather, it reflects a longstanding and deep-seated aversion in the United States to large government programs and American political culture generally."

There are many, many reasons why the US isn't a social democracy yet. It has to do with corporate influence, yes, but also the structure of our government, the views of our citizens, Congress's bias toward rural areas, and our long history of white supremacy. Merely taking the money out of politics, in other words, is nowhere near enough if liberals want to create a comprehensive welfare state. That's a much harder, longer, more arduous political project.

In addition to those quoted, thanks to Lee Drutman, Mark Schmitt, and Brian Schaffner for their help as I researched this piece. None is responsible for the argument, but all are owed my thanks.