A house divided? Sanders rebellion isn't about Democrats, really.

Maybe Republicans aren’t alone in facing division. As presidential primary season nears its end, Democrats are struggling with a party split between supporters of insider Hillary Clinton and the army of dogged insurgent Bernie Sanders.

It’s a gap that seems to be getting wider even as Mrs. Clinton closes in on clinching the nomination. Over the weekend, Sanders supporters allegedly tossed chairs and made death threats to party officials at a Democratic state convention in Nevada. The Democratic National Committee condemned these reported actions. Senator Sanders was less than apologetic in response.

Democrats will probably unite to oppose GOP nominee Donald Trump in the fall. That’s how both American political parties generally behave: When it’s game time, internal squabbles are left in the dressing room. Teammates come together to battle the larger threat of a partisan foe.

But in this election, that likelihood of things going to form for Democrats or Republicans is still only a “probably.” Sanders, an independent, has less emotional investment in the Democratic Party. Many of his voters are similarly minded.

The word “rigged” plays a large part in Sanders’s rhetoric about the economy. If large numbers of frustrated Sanders voters feel “rigged” applies to the Democratic nomination process as well it could presage trouble for the party in November.

Sanders himself expressed anger along these lines on Tuesday evening.

“The Democratic Party is going to have to make a very, very profound and important decision. It can do the right thing and open its doors and welcome into the party people who are prepared to fight for real economic and social change. This is the Democratic Party I want to see,” Sanders said during a campaign stop in southern California.

“Or the other option for the Democratic Party, which I see as a very sad and tragic option, is to choose and maintain its status quo structure, remain dependent on big money campaign contributions, and be a party with limited participation and limited energy,” Sanders said.

An unfair process?

Right now, Democratic emotions are running high. Sanders is continuing to win states – he won Oregon on Tuesday – and gives every appearance of mounting a challenge that remains vital. But that’s only on the surface. Clinton remains in control of the race, as she has almost from the beginning.

Her lead in pledged delegates, run up with big wins in the South and large Eastern states, remains substantial. The Democratic nomination process divvies up delegates proportionately everywhere, meaning Clinton can clinch the nomination even if she loses every remaining state contest. 

Meanwhile, those 712 superdelegates remain waiting in the wings. They’ve provided Clinton a psychological boost from the beginning. Technically unpledged, many endorsed her before voting even began.

Are superdelegates a way for the DNC to put its finger on the scale of the nomination process? It might look that way to a Sanders backer, even though Sanders would still lose if superdelegates were distributed in proportion to who won which state.

All this has raised the temperature of some Sanders backers high enough to boil herbal tea. In an April McClatchy-Marist poll, 25 percent of Sanders supporters said they would not back Clinton in the general election if she wins the nomination.

Sanders has won 10 million votes; if a quarter of his backers stay home in November we all might need to get used to saying “President Trump.” (Or maybe “President Mr. Trump.” All but his closest pals use “Mr.” when addressing him.)

What Bernie wants

But history indicates that the Democrats will unite, and those Sanders voters will see a Trump presidency as a greater danger. Similar percentages of Clinton voters said they’d never support Barack Obama in 2008. Yet they did, as Clinton endorsed him and campaigned hard. The way she handled her loss made a difference for the party.

Will Sanders be similarly loyal? Nobody knows. It depends how he sees his political future. Clinton knew she wanted to remain viable at the highest party levels. Sanders might not. He’s unlikely to run for president again or serve in a Clinton cabinet.

He certainly wants to advance his progressive vision, but how best to do that? On the inside, pushing for legislation? Or on the outside, serving as a critic and ideological influence?

“He’s aiming, perhaps, to be the permanent countervailing force in Democratic politics. The eternal burr stuck on the party’s lovely cashmere sweater,” said Clare Malone, a senior political writer at FiveThirtyEight, in a Tuesday chat about the state of the race.

Many Sanders voters might have a similarly weak attachment to the Democratic Party as an institution.

On the one hand, they’re closer to Clinton voters in terms of ideology than you might think. 

Clinton and Sanders supporters have similar views on a wide range of issues, according to Pew Research data published in March. They’re within a few percentage points of each other in disapproving of more scrutiny for US Muslims, opposing cutting Social Security, supporting government involvement in health care, and saying free trade is good for the country. 

Yes, Sanders is running to Clinton’s left on specific issues such as free college tuition and single-payer health care, but Clinton herself is left of where husband Bill was in 1992. Self-described liberal voters aren’t a rock-solid Sanders constituency, as young voters are.

The 'Democrats' who aren't Democrats

But on the other hand, Clinton and Sanders voters differ markedly in one important respect: partisanship.

Clinton’s supporters are far more likely to be registered Democrats. She’s won self-identified party members in the vast majority of states contested so far. That makes sense – she’s one of them. She’s been a party stalwart for a generation.

Sanders supporters are far more likely to be Democratic-leaning independents. This is a good-sized chunk of the electorate. About one-third of US voters identify as independent, and one-third of them are really Democrats who just don’t like labels. Sanders has dominated with these voters virtually everywhere.

Will this weaker partisan identity cause disgruntled Bernieites to stay home in November? That may be the key question.

It’s also why the word “rigged” could be so powerful. Non-Democratic liberals may be more prone to see closed primaries, in which only party members vote, as cheating. Clinton has dominated closed primaries; Sanders has done better in open primaries and caucuses.

They might also consider existing, and complicated, party procedures as illegitimate. That appears to be what happened in Nevada, where a multi-level delegate selection process worked in favor of a Clinton operation backed by Senate minority leader Harry Reid, a legendary Nevada political figure.

Rogue Sanders voters probably won’t bolt for Trump. At least, few will, no matter what those Bernie Bros are threatening online. Both candidates are running campaigns defined as populist. But Sanders and Trump voters are far different when it comes to most issues.

Sanders voters are pro-immigration and vehemently oppose Trump’s proposed wall and his proposed temporary ban on non-citizen Muslims entering the country. A majority of Sanders backers think free trade is good for the US, while Trump denounces it as a job killer. Ninety-one percent of Sanders voters think the US economic system favors the powerful, according to Pew data. Only 45 percent of Trump voters agree.

No, if the Democratic Party does experience a substantial split on Election Day, it will be because Sanders supporters just aren’t at the polls. And that’s a future Sanders can greatly influence with his own behavior in the campaign endgame and at the Democratic National Convention in Philadelphia.