One month out from the Iowa caucuses, the race for the Democratic nomination looks remarkably stable. Joe Biden is solidly in the lead, Bernie Sanders is roughly nine points behind him, Elizabeth Warren and Pete Buttigieg have faded, and Michael Bloomberg is blowing through wads of cash in order to stay inches ahead of Amy Klobuchar and Andrew Yang.

The dynamics of the race have been consistent at the top for more than a year now. Unless something changes soon, Biden is going to prevail. Which means that Sanders will not. And that could be a major problem for the party.

Will Sanders supporters be willing (for the second time in as many presidential election cycles) to hold their noses and turn out to vote in November for a card-carrying member of the Democratic Party establishment when the socialist to whom they're so passionately devoted falls short of victory? Or will they be inclined (in much greater numbers than they did in 2016) to stay home or support someone's third-party bid from the left in a deliberate attempt to sink a party for which they have burning contempt? Those questions are going to become increasingly important as events unfold over the next few months.

Of course, the opposite could also become a problem. If Biden sinks and Sanders somehow manages to rise above 20 percent in the polls (he hasn't been higher than that since last April) and ultimately win the nomination, the more moderate voters backing Biden will need to decide if they can stomach casting a ballot for the most left-wing candidate ever to become a major party nominee.

But there is one very important difference between Biden and Sanders voters. The former are supporting the former vice president primarily because they think he is well-poised to win in a general-election contest against Trump. There's very little sign of fervent devotion to Biden as a person or a candidate. This indicates pragmatic flexibility that may be compatible with rallying behind another nominee, even if he's a socialist promising $97 trillion in new government spending.

The same cannot be said for Sanders supporters, who are uncompromisingly devoted to the Vermont senator and passionately committed to undertaking what he breathlessly describes as a “political revolution.” The Atlantic's Derek Thompson is right to suggest that these millennial (and younger) voters effectively constitute a third, firmly left-wing party in American politics. This party is happy to turn out for the Democrats so long as Sanders is its nominee. But if it's bumbling, stumbling Biden — a man who served for eight years as a right-hand man to a lukewarm, moderate president after decades of representing a state (Delaware) dominated by credit card companies — well, then all bets are off. (Even if you believe polls that show a decent number of Bernie voters would shift to Biden as their second choice, this would still leave an awful lot of unhappy and homeless Sanders supporters around to stir up trouble.)

It would be one thing if 2016 had never happened. But it did, and many of Bernie's supporters feel like they got burned badly by the Democratic establishment not once but twice four years ago. First, their hopes were raised by Sanders' surprising success across the country and then dashed by his inability to overcome Hillary Clinton's strong institutional support. Then they settled for Clinton as a consolation prize in order to defeat Donald Trump in the general election only to have her lose to him. As far as they're concerned, they've been fooled two times already.

It's passion that explains Sanders' incredible success at fundraising — with $34.5 million for the fourth quarter of 2019, a number that is likely to dwarf everyone else's in the race. It's even more impressive when we factor in the Sanders campaign's emphasis on collecting small donations. That shows a lot of devotion by a lot of people.

So far there's no sign that it's enough people to win the race for the nomination. But it would be more than enough to torpedo Democrats' chances of taking down Trump in November. Will Sanders (an independent who only calls himself a Democrat when he's running for president) urge his supporters once again to back the Democratic nominee, even if it's Biden? And even if he does, will those supporters go along with such an unrevolutionary act of sail-trimming?

That would be the real test of whether Sanders is leading a cult of his own personality or a genuine, ideologically galvanized movement that will outlast his leadership and continue to influence the shape of American politics going forward.

A movement firmly committed to bringing about the scale of changes Sanders has been advocating wouldn't hesitate to “heighten the contradictions” — that is, allow things to get worse in the short term (by acting in a way that helps Trump to win a second term) in the hope that better long-term prospects for progress (namely, a big shift to the left in the electorate) would emerge from the mess. If nothing else, a second loss to Trump would ensure the overthrow of the establishment that has led the Democratic Party since 1992, thereby opening up the prospect of its takeover by left-wing populists by 2024.

As I've pointed out before, the Democratic electoral coalition is extremely broad, and perhaps too broad for its own good. A party that's big enough to include everyone from socialist Bernie Sanders to liberal Republican Michael Bloomberg is a party that will struggle to find a single standard-bearer who can unite its disparate factions. It might even be a party poised to shatter into its constituent parts.

The Sanders campaign may well end up being the catalyst that prompts the detonation.