Twelve years ago, an insurgent challenger riding a wave of political momentum ran into a brick wall in New Hampshire. Barack Obama rediscovered his mojo in South Carolina, but for two weeks, it wasn’t clear where his campaign and his story were headed.

It’s too early to know where this Democratic story is headed in the fight to unseat Donald Trump. But some things are already clear.

The first is that Joe Biden’s campaign is on life support. Not so long ago, this was Biden’s contest to lose. After two crushing defeats, there’s no doubt about the prognosis: the former vice-president is fading fast.

Back in 2008 and 2016, Hillary Clinton ran two versions of the argument that voters wanted a mix of experience and change: of looking back and looking forward. That argument failed among Democrats the first time, and won the national popular vote the second time around by a large margin.

But it has resoundingly failed amid the wreckage of Donald Trump’s presidency, just as it did amid the carnage of George W Bush’s. Democratic voters want more change, not less change. Biden likes to say that we should compare him to the alternative, not the almighty. Sadly the voters have made the comparison and found him wanting against both.

“When I die, I want to be reborn in Charleston,” Biden said on Tuesday, having quit New Hampshire for South Carolina well before his defeat was final. Rebirth is a wonderful concept but probably not the best image to invoke when your campaign is flatlining.

New Hampshire buried not one but three campaigns besides Biden’s. Elizabeth Warren had built a brilliant campaign around her many policy proposals until she ran into the brick wall of trying to make sense of Bernie Sanders’ signature idea: Medicare for All.

Who knew it would be so hard to make the math work to avoid taxing everybody while also massively expanding government healthcare? It’s much easier to keep people excited about abolishing private insurance if you don’t talk about taxes.

Tuesday’s results were bad news for math in general. Andrew Yang campaigned on math and facts with his platform of universal basic income. But the math and the facts of the votes pointed to universal basic failure. At least Yang qualified for multiple debate stages to make his quirky case. Senator Michael Bennet of Colorado dropped out of a race in which few voters knew he was even running.

If Iowa left us with a hot mess of mathematics, New Hampshire leaves us with a three-way contest between an old socialist man, a young centrist man and a middle-aged centrist woman. With an old centrist billionaire waiting to join this cluster, it’s time to admit that this field remains too crowded for anyone’s comfort.

The headlines may tout the impressive third place for Amy Klobuchar, the Minnesota senator who seemed like an afterthought in so many TV debates. But a bronze medal does not create momentum, even if you call it a Klobucharge.

A man walks past a sign for Joe Biden lying on the ground on the day of New Hampshire’s first-in-the-nation primary in Nashua, New Hampshire. Photograph: Carlos Barría/Reuters

In particular it’s hard to see how she builds support in the vastly less white states of Nevada and South Carolina, where our three-way leaders travel next. The same goes for Pete Buttigieg, the small-town mayor who secured a fine second place in New Hampshire and a debatable first place in Iowa.

Which leaves us with one candidate with a national following, and another candidate with the ability to buy a national following.

Bernie Sanders won New Hampshire with a surprisingly narrow margin of victory, and is now the undoubted frontrunner in this contest. But his campaign staff – if not his fervent fans – should be deeply troubled by some of the underlying data.

Far from driving out high turnout, Sanders has not attracted waves of new, younger voters in Iowa and New Hampshire. According to the CNN exit poll, just 12% of New Hampshire voters were first-timers, and just 11% were under 30 years old. All this in a state he won by 22 points four years ago, a stone’s throw from his home base of Vermont.

Democrats may be concerned about the apparent weakness of every frontrunner that has passed into pole position. But the underlying numbers suggest something very different. According to the CNN exit poll, six in 10 Democrats want above all a candidate who can beat Trump.

Why is it so hard to settle on who that might be? Well the polls suggest there are several candidates who would do just that. The most recent Quinnipiac poll this week showed every single prominent Democrat with a commanding lead over the commander-in-chief, from Bloomberg (nine points) and Sanders (eight points) to Klobuchar (six points) and Buttigieg (four points). Even the mayor of the great metropolis of South Bend, Indiana, beats Donald Trump.

Of course, none of those candidates have yet suffered the full onslaught of the billion-dollar disinformation campaign that Trump is yet to unleash. Except for Joe Biden, of course. And he still beats Trump by 50 to 43 points.

With so much opportunity, and frankly so much fear, Democrats are shopping around for their best bet to beat the biggest bozo. They don’t seem to care about the ideology or character of their candidate as long as she or he isn’t a white nationalist with the attention span of an amoeba.

That’s why the Minnesota senator started her non-victory speech by saying, “Hello America. I’m Amy Klobuchar and I will beat Donald Trump.” Subtle, this is not.

In three short weeks, this race will shift from window-shopping to the big-ticket purchase of Super Tuesday, when one-third of the party’s delegates will be awarded across expensive states like California and Texas.

The days of split decisions between three or four candidates are coming to an end. This contest will come down to two Democrats: Bernie Sanders and one other. The only question is who the un-Bernie will be, and whether the party can live with the results of a protracted head-to-head fight.

Elizabeth Warren delivered her losing speech along those lines, reinventing herself one last time as a unity candidate, and lamenting the personal attacks of these primary weeks. “These harsh tactics might work if you’re willing to burn down the rest of the party in order to be the last man standing,” she warned. “We cannot afford to fall into factions. We win when we come together.”

Maybe so. Or maybe these factions will all come together thanks to the ultimate unity candidate who brings every Democrat together: Donald Trump.