Bernie Sanders fans may not love Hillary Clinton. But they won't vote for Donald Trump.

Democrats hoping to bring the party together after a bitter and contentious primary between Hillary Clinton and Bernie Sanders may have found their answer: Donald Trump.

Trump has become the presumptive Republican nominee after rivals John Kasich and Ted Cruz suspended their presidential campaigns.

From the perspective of Democratic Party unity, Trump's march to the nomination is great news: Sanders's supporters have made a lot of noise about going "Bernie or bust," but a poll out from CNN on Wednesday finds they prefer Clinton to Trump by an 86-to-10 margin.

Sanders voters in new CNN poll favor Clinton over Trump 86-10. Non-Trump GOP voters favor Trump over Clinton 70-24: https://t.co/duFYabvlHc

— Alan Abramowitz (@AlanIAbramowitz) May 4, 2016

That's about the same ratio of Clinton supporters who voted for John McCain over Barack Obama in 2008, according to Emory political scientist Alan Abramowitz. And it's still early: As we move to the general election, Abramowitz says, Democrats are even more likely to swing behind their nominee.

"The reality of staring at Donald Trump over there as the Republican nominee, now that that's settled, I think will do wonders to concentrate the minds of Democrats," Abramowitz said.

The CNN poll found less reason to believe Republicans would unify around their nominee. In it, only 70 percent of Republicans who backed another candidate said they would support Trump, while 24 percent of them said they wouldn't.

Why experts think "Bernie or bust" will probably go bust

Back in March, I interviewed two experts — Abramowitz and Matt Grossmann, director of the Institute for Public Policy and Social Research at Michigan State University — who said they thought "Bernie or bust" is unlikely to have much of an impact.

(Photo: JEWEL SAMAD/AFP/Getty Images)

Many of Sanders's supporters have insisted that they'll never support Clinton. In one poll, for instance, 33 percent of Sanders voters say they won't vote for Clinton, and more than 90,000 people have already signed a pledge to that effect.

But here are some of the key reasons the political scientists gave for thinking the Democratic Party will eventually come together:

They mostly agree on big policy questions: Sanders and Clinton may seem at odds right now, but they stand an ocean apart from the major Republican candidates on an overwhelming number of positions.

"The differences between Sanders and Clinton on policy just aren't very great, and they get blown out of proportion in a primary contest," Abramowitz said.

There are far too many to list here, but a sample include: the need to raise taxes on the wealthy, the reality of climate change, appointing a progressive to the Supreme Court, the desire not to deport millions of undocumented immigrants, and raising the minimum wage.

A (relatively) civil primary: Sanders and Clinton have traded some barbs over their past voting records, and Sanders has knocked her for taking exorbitant speaking fees from Wall Street.

But the primary hasn't been that acrimonious. "On our worst days ... we are 100 times better than any Republican candidate," Sanders said in February. There have been few attacks driven by the candidates' personalities or personal histories.

"The race hasn't been very bitter — much less bitter than that between (Barack) Obama and Clinton, for instance," Grossman said.

Sanders himself: Sanders himself has pledged to back Clinton if he loses the primary, reiterating in March that both candidates' key goal must be to not allow the Republicans to win back the White House.

.@BernieSanders: "Hillary Clinton and I agree that it is absolutely imperative that no Republican make it to the Oval Office."

— Sahil Kapur (@sahilkapur) March 26, 2016

This effect will be even more powerful if Sanders gives a major speech at the Democratic National Convention urging his supporters to rally behind Clinton, Abramowitz noted.

Historical precedent: In July 2008, 54 percent of Clinton voters said they wouldn't support Barack Obama in a general election. (They even had a nickname, "PUMAs" — "party unity my ass," the 2008 analog to today's "Bernie or bust-ers.")

Ultimately, however, nine in 10 Democrats ended up voting for Obama over John McCain, according to the Nation. Similar threats were made — and later failed to materialize — from the supporters of Howard Dean in 2004, according to Abramowitz.

"Just about every time there's a closely contested nomination battle, the supporters of the candidate who appear to be losing threaten to walk out," Abramowitz said. "Then they don't."

What are the reasons to believe this conventional wisdom is wrong?

Is there any reason to believe that something will be fundamentally different this year?

One argument advanced by Sanders's supporters is that we're in an "anti-establishment" year — in which both primary electorates are ignoring cues from party leaders — and that the independents who have flocked to the Vermont senator are therefore unlikely to support Clinton, the consummate insider.

Another possible variable is that young people, who have thrilled to Sanders in huge numbers, will feel less of an allegiance to stay within the Democratic Party and support its nominee. That makes their support for the nominee less likely to be a sure bet.

"Young people are certainly less tied to the political parties in general," Grossmann says. "They're less likely to have stable partisan voting patterns, and that makes them more likely to be open to alternatives."

Democrats' support for Obama should help Clinton unify the party

There is one scenario in which the supporters of a losing primary candidate tend to really not support the party's nominee: when an unpopular presidential incumbent faces a tough challenger.

"When you see an incumbent president seeing a serious challenge for the nomination, that's always a bad sign," Abramowitz said, noting that primary challenges against Gerald Ford in 1976 and Jimmy Carter in 1980 both reflected their weakness in the general election.

I asked Abramowitz if this year could prove another iteration of this basic dynamic. After all, isn't Clinton largely running for Obama's third term?

He rejected that notion out of hand. Yes, Clinton has run under the banner of Obama's third term — but that should help, not hurt, her efforts to unify the party, he said.

"Obama is actually very popular among Democrats," Abramowitz said, noting the president has a nearly 90 percent approval rating among members of his party. "If there were more discontent among rank-and-file voters with Obama, there would be more opportunity for an anti-establishment candidate in the general."

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