Could Klobuchar or Buttigieg be the best hope for centrist Democrats?

The American presidential campaign marathon is a grueling and seemingly endless experience, for candidates and voters alike. Already it seems to have gone on for ever and yet we’re still more than a year away from the election. But the value of this protracted ordeal is that it does make the candidates stronger and better campaigners. And by the time this fourth official Democratic debate had concluded, there was a glimmer of clarity as to how the race is likely to sort itself out.

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The big takeaway is that while many Americans still consider former vice president Joe Biden to be the frontrunner — and he’s still leading in some polls — the candidates themselves now see Elizabeth Warren at the head of the pack. That was reflected in several of them launching salvoes against her for the first time, which in turn gave her the most opportunities to respond and thus more speaking time than any other candidate.

Warren handled the attacks well for the most part. She looked evasive at the start of the debate when she refused to acknowledge that her Medicare for All plan would raise taxes for middle-class voters, saying only that their overall costs would go down. But for the rest of the time she projected a front-runner’s loftiness, shrugging off the barbs of her rivals and focusing on making a case against Donald Trump and the capitalist status quo. She even reprised her 2011 speech about how wealthy people in America got rich in part because of government services paid for by the rest of society – an argument that then-president Barack Obama garbled the following year as, “You didn’t build that.” Warren didn’t sparkle in this debate as she has in the past, but neither did she stumble in any important respects.

Bernie Sanders also had a successful performance, in part simply because he appeared undiminished by his recent heart attack. As in previous debates, he offered up red-meat socialist rhetoric about the need for a revolution to unrig the capitalist system, and also called for breaking up large media and agribusiness companies as well as tech companies such as Amazon. But he came across as less abrasive than in some past debates and received warm applause for his thanks to all who reached out to him during his hospitalization.

Biden had his best debate so far, largely because he was out of the line of fire and for the first time had a largely gaffe-free performance. He didn’t offer a detailed defense of his son’s business dealings in Ukraine, but did forcefully maintain that neither he nor his son had done anything wrong. More importantly, for the first time he actually managed to make an affirmative case for his candidacy. He touted his age and experience as critical components of wise presidential leadership, boasted that he had more substantive legislative accomplishments and persuasive ability than all the other candidates, vowed to restore middle-class prosperity, and dismissed Warren’s and Sanders’ plans as impractical and vague.

The sharpest criticism of Warren-Sanders progressivism, however, came from Amy Klobuchar and Pete Buttigieg. Klobuchar, despite her Minnesota-nice affect, severely rebuked Warren’s often-repeated claim that anyone who disagrees with her plans is gutless and/or retailing Republican talking points, and also went after Andrew Yang for seeming to characterize Putin’s Russia and the US as morally equivalent. Buttigieg, too, hit Warren and Sanders for taking away Americans’ freedom of choice in health insurance and also had a sharp exchange with Tulsi Gabbard, calling her “dead wrong” for wanting US troops to leave Syria.

Related: Elizabeth Warren was attacked from all sides in debate – and she barely batted an eye | Moira Donegan

Klobuchar and especially Buttigieg proved more adept than Biden at making a coherent case for Democratic moderation — meaning not Hillary Clinton-style neoliberalism so much as a concern for pragmatism, social cohesion, US world leadership, and at least some measure of bipartisanship. If Biden continues to sink in the polls, they have a chance to rise to top-tier status.

None of the other candidates appear to have had the kind of breakout performance they needed, and the launch of the House impeachment inquiry of Donald Trump (which all the candidates supported) doesn’t seem to have changed the basic dynamic of the contest. So the rest of the campaign is likely to boil down to whether Biden, Buttigieg or Klobuchar will emerge as the top moderate candidate; whether Warren or Sanders will emerge as the progressive candidate; and who then ultimately will become the nominee. But it’s likely to be a long time indeed before any of these questions are answered definitively.

• Geoffrey Kabaservice is the director of political studies at the Niskanen Center in Washington, DC