BY FAR the biggest question going into the second, more high-powered, instalment of this week’s Democratic primary debate on June 27th concerned Joe Biden. The 76-year-old former vice-president took a big lead in the race the moment he entered it—despite two lamentable previous presidential runs and rumours that he might lack the requisite energy for a third. His campaign’s subsequent efforts to shield him from reporters increased that suspicion. The debate in Miami, in which Mr Biden appeared alongside nine other candidates, was his first big opportunity to allay it. He failed that test so resoundingly that his performance was at times painful to watch.

Mr Biden’s campaign pledge is to take America back to how things were under Barack Obama, whose enduring popularity on the left, especially among non-white voters, is by far his biggest advantage. That and a feeling that his centre-leftishness would be a safer bet against Donald Trump than the fiery leftishness of Bernie Sanders and Elizabeth Warren, who are currently in second and third place respectively, explains his lead in the polls. His potential disadvantages are that, as many Democrats have moved to the left, those moderate Obama-era positions, on immigration, foreign policy, health care and so forth, are no longer all that popular among Democratic primary voters. The hard-left hates them. And Mr Biden may not be up to dealing with the brickbats this guarantees him. His lifelong prolixity has not improved with age. Where once he sounded unfocused, he now sometimes sounds befuddled. He can also sound strikingly incurious about the many ways America is changing—which in turn makes his status-quo-ante solutions appear complacent and out-of-touch.

Those weaknesses were apparent in Miami from the start. He delivered semi-prepared answers on health care and foreign policy that were rambling and at times hard to follow. When the candidates were periodically asked to raise their hands if they agreed with one assertion or another—that crossing into America illegally should not be a crime, for example—he kept raising his halfway, as if he was unsure what he thought of the issue, or what the rules were, or maybe he was just frail. A couple of his answers suggested he had not correctly heard the question. What would you do on your first day in the Oval Office, he was asked? “I would defeat Donald Trump!” he replied.

These difficulties made Mr Biden’s frequent recourse to trumpeting his connection to Mr Obama sound evasive at best. The debate also showed how vulnerable he is, as a result of his decades-long career and frequent gaffes, to attacks on his record. Senator Kamala Harris, one of his main rivals for all-important African-American voters, eviscerated him over his long-ago opposition to integrating schools by “bussing” in black pupils—and for his recent fond reflections on what it was like to work alongside old-style Democratic segregationists. Adding insult to injury, she contrasted Mr Biden’s apparent carelessness towards minority sensibilities with a memory of the racism she had faced as a mixed-race child in California.

The performances of Ms Harris and Pete Buttigieg, Mr Biden’s two closest rivals on the stage after Mr Sanders, were indeed more bad news for the former vice-president. Both were impressive, with the debate format playing to Ms Harris’s strengths especially. A former prosecutor, she has courtroom presence (she knows how to grab attention by slowing down her speech where others speed up). And—as she showed in her exchange with Mr Biden—she thrives on the cut and thrust.

She has been less impressive on the trail; she seems overly cautious and unable to give a clear sense of her politics. That is a failing she appeared to repeat, rather ludicrously, during the debate. When the candidates were asked who among them would abolish private health-care insurance, she joined Mr Sanders in raising her hand. This was a hard-left position she had previously claimed to support in a television interview, but then rowed back from. The fact that she was now readopting it looked like the biggest policy news of the night. Immediately after the debate, however, Ms Harris said she had again made a mistake. That would again be a sensible course correction: the policy looks like a general-election loser. More broadly, however, Ms Harris’s strong showing confirms an impression that she may be the candidate most likely to gain if Mr Biden slides.

Mr Buttigieg could also gain. His performance showed what a rare talent the upstart mayor of South Bend, Indiana, is. Unlike Mr Biden, he is able to make pragmatism sound interesting. More important than any candidate’s health-care policy is how they intend to achieve it, he said. He also dealt skilfully with a potentially damaging controversy he is mired in back in South Bend—a police killing that has turned members of the city’s black community against him. “It’s a mess, and we’re hurting,” he acknowledged. Asked why the city’s police force remains overwhelmingly white, despite his efforts to introduce more diversity, he grimaced and said, it was “because I couldn’t get it done.” Besides being appealing, Mr Buttigieg’s modesty is tactically useful. It makes him hard to attack.

Mr Sanders put in a quieter performance. Apparently far more vigorous than Mr Biden—whom he is older than by a year—the democratic socialist remains an effective debater of his own left-wing economic policy ideas. And he has a clear message—on the inequities of the system and the need for massive spending schemes to fix them— that a sizeable minority of Democrats want to hear. But there are not enough of them to win the primary. Mr Sanders’s success in 2016 (not that he ever seriously threatened to beat Hillary Clinton) was based on attracting voters who were chiefly repelled by his establishment rival, and they have a greater array of alternatives this time around. He has been sliding in the polls, most conspicuously to the benefit of Mrs Warren and Mr Buttigieg. He probably cannot win without broadening his message and appeal: his debate performance showed how unlikely that is.

The next big question concerns whether Mr Biden will actually suffer for his poor performance. It is hard to imagine he will not. The former vice-president simply does not look like the safe bet many Democratic voters appear to want. Then again, he never really has. Perhaps he will maintain his lead. Whether he does or not, however, it is hard to be relaxed about the Democrats’ chances of beating Donald Trump in 2020.

Short of a major economic downturn, centre-left moderation still looks like the likeliest means to winning a general election next year. And Mr Biden is currently a poor proponent of it. None of the other avowedly moderate candidates looks competitive—including, on the stage in Miami, Senator Michael Bennet, who offered further evidence that he is smart and sensible; just not charismatic. Meanwhile, Mr Biden’s closest rivals—Mr Sanders, Ms Warren and Ms Harris—have all, to varying degrees, rejected moderation altogether. That may turn out to be the most important takeaway from this week’s opening debates. Unless, that is, Ms Harris really didn’t mean the hard-left shift on health-care policy that she appeared to signal. Hopefully she didn’t.