Bernie Sanders is getting badly hurt at the ballot box by an idea his supporters think is deeply misguided.

According to exit polls, Hillary Clinton has clobbered Sanders among voters who said a candidate who "can win in November" is their top concern. Even in New Hampshire, a state Sanders won in a landslide, Clinton beat Sanders among these voters by 59 points.

For many Clinton supporters, picking Sanders just sounds like a reckless gamble. The idea of nominating a little-known "democratic socialist" from Vermont seems like a sure way to guarantee that Republicans take back the White House with little upside for Democrats.

Sanders's fans think this is nonsense. To them, arguments against the candidate on "electability" grounds are worse than a distraction from more important policy questions: They also miss clear evidence that Sanders, not Clinton, would be the stronger candidate against Republicans.

This disagreement has had people talking past each other since the beginning of the campaign. But regardless of who you think is right, the fight actually reveals quite a lot about the fault lines of the primary — and the worldviews of the competing candidates.

Sanders supporters point to general election polls against Republican candidates

Several polls have found Sanders having a better shot than Clinton in one-on-one general election matchups against Donald Trump, Marco Rubio, or Ted Cruz — sometimes by healthy margins.

These polls are frequently cited in columns arguing that Sanders is a better general election candidate, including one by Princeton history professor Matt Karp. Writing for Jacobin, Karp pointed to The Timeline of Presidential Elections, a book written by Robert S. Erikson and Christopher Wlezien, to argue that polls "as early as April have generally produced results close to the outcome in November."

But that really evades the core of Erikson and Wlezien's findings. In fact, those authors conclude that "polls from the beginning of the year … have virtually no predictive power," according to an online summary of the book.

In an interview, Erikson told me that general election polling from this time of year is "pretty meaningless," and said he was surprised his work had been cited to argue for Sanders's general election chances.

"Bernie can look good in some polls, but I don't think anyone who follows politics thinks those would hold in November," Erikson said.

It is for this reason that some, like Seth McKee, a political science professor at Texas Tech University, regard such early polls as "absolutely worthless." Relatively few voters have made up their minds this long before the election, McKee says.

Then there's the point raised by the Washington Post's Philip Bump: that even if you take these polls as meaningful — which Bump doesn't — it's not clear they show Sanders has an advantage.

In Quinnipiac's head-to-head polling, Bump says, Clinton beats Rubio and Trump and ties Cruz. Sanders, by contrast, beats Trump but loses to both Rubio and Cruz.

Sanders's supporters: Clinton is just much less popular with the electorate

Beyond the general election polls, Sanders's supporters also frequently point to the candidates' favorability ratings. And with good reason: It seems blindingly obvious that the candidate who is seen as more favorable by more people would do better in a general election.

"The candidate with the higher favorability always wins — and no one with unfavorable numbers higher than their favorables ever wins," writes one columnist at Daily Kos. "Right now, Clinton's favorability numbers are low and underwater."

Glenn Greenwald at the Intercept hammers this point home, citing polling data showing that Clinton is much more likely to be viewed unfavorably in polls than Sanders.

There's a Quinnipiac poll that puts Sanders's national favorability with registered voters at 51 points to Clinton's 37 points. In Ohio, Greenwald notes, Sanders's favorability rating is 44 to 41; by contrast, Clinton's favorable-unfavorable rating in Ohio is negative 20 points — 37 to 57.

Given the polling data, Greenwald says, putting the onus on Sanders to prove his general election viability seems unfair. Why should the burden of evidence fall on Sanders's fans to prove he's the stronger general candidate, when so much of the polling points in his favor?

"The pundit consensus ... is that Hillary Clinton is electable and Bernie Sanders is not. There’s virtually no data to support this assertion. All of the relevant data compels the opposite conclusion," Greenwald writes under the headline, "With Donald Trump Looming, Should Dems Take a Huge Electability Gamble by Nominating Hillary Clinton?"

The solution to Clinton's unpopularity, Sanders's supporters say, is someone outside the establishment who excites the base

For Clinton's supporters, the response to this argument is clear. They say Clinton has higher unfavorable ratings because she's been in the public eye for longer, and has thus been subject to many more attacks that have damaged her reputation.

But to Sanders's supporters, Clinton's low favorability ratings aren't a result of fighting Republicans too strongly. They're a sign of the opposite: an indication of her ideological compromises, of her compromised dealmaking, and of her complicity in a corrupt system controlled by financial interests.

This diagnosis of Clinton's problem is also contrasted with Sanders as the cure: Democrats can win with a pure, independent candidate who will bring an untapped swath of the American electorate into the voting booth.

"Bernie is the kind of authentic and inspirational candidate who could move millions and millions of Americans — both hard core Democratic base voters and new voters — to show up in November 2016," writes Tad Daley at CommonDreams. "How many people do you know who feel the same kind of passion and intensity about Hillary Clinton?"

To these supporters, Donald Trump's rise in the Republican race proves that the electorate is hungering for someone who stands outside of Washington.

"As loath as I am to mention Sanders and Trump in the same sentence, the popularity of both stems from a growing consciousness and anger among the American working class that they’ve been screwed over by the establishment," writes Jamie Peck at Death and Taxes.

You don't have to be in Sanders's corner to think there may be something to this.

Sanders has generated much more enthusiasm than Clinton by multiple metrics, including the size of his campaign rallies and the record-breaking size of his small-dollar donor network. And there's certainly reason to believe that Democrats have done much better in recent midterm elections when they pick candidates who run on strongly progressive campaigns and motivate the base.

"There is precious little evidence to suggest that progressive populist campaigns have hurt Democratic candidates in the past decade. In fact, the reverse has been true," says David Atkins at Washington Monthly. "Most modern elections are base elections, and base-oriented populism has proven quite effective in recent years."

Why Clinton's supporters and most pundits think Sanders's electability argument misreads American politics

Unlike Sanders's supporters, Clinton's fans (and most pundits) see her low favorability ratings differently: as the necessary price of fighting for liberal causes in a country where 38 percent of people call themselves conservatives.

"All politicians get battered the more they're known. Maybe that won't happen to Bernie, but I think it will," said Joan Walsh, a columnist at the Nation and a Clinton supporter, on WNYC. "[Sanders] hasn't spent 25 years in the spotlight being trashed by what I would also call the vast right-wing conspiracy."

This is where Clinton and Sanders supporters tend to have very different understandings of partisan politics. For those backing Clinton, her low favorability ratings are evidence that she has fought for a set of ideas that nearly half of the country opposes.

As Mother Jones's Kevin Drum writes: "Republicans hate Hillary, Democrats love Hillary, and independents are unsure. It may well be that Hillary Clinton has an image problem that she needs to work on, but it's pretty much the same image problem she's had forever."

This jibes with what many election experts in the field believe: that Clinton's high unfavorable ratings are largely a function of her prominent public image.

"I subscribe to the conventional notion that Sanders hasn't been attacked in mainstream discourse by the Republicans," said Julia Azari, a political science professor at Marquette and a Vox contributor. "She has higher name recognition, she's been in public life for a long time, and people have formed distinct impressions of her."

Why many believe Sanders is far less electable

Political scientists don't purport to know for certain which candidate would do better in a general election.

But they say the body of evidence we have suggests voters choose the candidate closer to them on the ideological spectrum, and the evidence shows that Sanders is more likely to be viewed as being further to the left than Clinton.

"[Sanders's] political views are more toward the ideological pole than the average voter's," John Sides, a professor in political science at George Washington University, told me for a prior story. "Absent a very favorable set of conditions, nominating a candidate like Sanders as opposed to a more moderate Democrat creates the risk of a penalty at the ballot box."

A full 50 percent of the electorate says it wouldn't vote for a socialist, according to Gallup. That's higher than the number who said they wouldn't vote for a Muslim (38 percent) or those who wouldn't vote for an atheist (40 percent).

This is really the core of Clinton boosters' argument: not that independents will flock to the former secretary of state, but that Sanders is just too large an ideological deviation from the center of American politics.

"The Clinton campaign, welcomely, does not depend on obliterating a longstanding American consensus about socialism in the middle of an election campaign. It does not require voters to imagine a European utopia that few have experienced and fewer still can envision here," writes David Faris at Indy Week. "American voters do not march to the polls to endorse theoretical visions of other countries."

What this fight shows about the deeper divisions in American politics

Karp, the Princeton history professor writing at Jacobin, suggested that this ideological reading of the public may miss Sanders's broad appeal.

"As political scientists Shawn Treier and D. Sunshine Hillygus have argued, two-dimensional surveys of voter ideology do not provide a useful guide to the American electorate," Karp writes as part of his broader argument, which is worth reading in full. "To the great disappointment of the Post editorial board, many self-identified 'moderates' are not sober Beltway centrists but in fact 'cross-pressured' by a mix of strong liberal and conservative beliefs."

But in an interview, professor Hillygus said that her research does not suggest that Sanders would be a better general election candidate.

Hillygus's research did show that there's a section of the American electorate open to a message beyond the typical left-right categories. But that's because some are voters whose views represent a mixture of liberalism on some issues and conservative on others, in a way that doesn't match with either party's current platforms.

She said her research does not suggest that there's a big chunk of the electorate eager to vote for someone perceived as being far to the left on all fronts.

"In contrast to the interpretation that a diverse set of issues will benefit Bernie Sanders, I actually think Sanders will have a more difficult time appealing to those people who have inconsistent ideologies, because he's further left and far more consistent," Hillygus said.

When Sanders's campaign was still in its infancy, drawing big crowds and record-breaking donations, one really could argue that Sanders was tapping into a new force in American politics that could help win the general election.

Clinton's string of big victories in the primary means that case is much harder to make. If the sleeper constituency for democratic socialism isn't big enough to win the Democratic nomination, why should voters believe it's big enough for the general election?

There's one answer to this question that squares with what many of Sanders's supporters believe: that undemocratic, elite influence is more to blame for Sanders's failure to win the nomination than anything related to his message.

"The Democratic establishment doesn’t want a Democrat as president – it specifically wants Hillary Clinton as president," writes Brogan Morris in Paste Magazine. "And so a myth has been concocted in a pro-Clinton environment, that Clinton is the ‘pragmatic’ choice, the one that you as a Democrat simply have to vote for if you want to beat the GOP."