The president of the United States proved himself capable of speaking in complete sentences during a press conference Thursday night.

This was notable because, before the presser, President Joe Biden’s competence at the most rudimentary aspects of public speaking had come into doubt. At both the first presidential debate in late June and his interview with ABC News last week, Biden repeatedly failed to produce coherent English on command.

In a perfectly rational world, the abysmal quality of Biden’s previous public performances should have raised the bar for him at Thursday’s press conference: If you just demonstrated that you’re a dreadful candidate at your worst, then winning your party’s confidence should require showing that you are an absolutely brilliant one at your best. Otherwise, why should your co-partisans tolerate your manifest unreliability?

But this is not how all Democrats see things.

Many in the party are reluctant to publicly defy their president, who has made his desire to stay in the 2024 race clear. And they also have little faith in Vice President Kamala Harris, who is by far the most likely Democrat to replace Biden at the top of the ticket. For these reasons, some Democratic lawmakers would like to believe that the case for Biden to step aside isn’t crystal clear. But the president’s disastrous debate performance forced such Democrats to entertain the idea that Biden was an anchor around their party’s neck. As the press revealed that Biden had been suffering such mental lapses with increasing frequency — and polls showed the president and his party slipping — the ranks of the rebellion-curious swelled. Before Thursday’s press conference, CBS News reported that “dozens” of congressional Democrats were considering calling for Biden’s exit after the event.

Yet some of these reluctant rebels evidently found cause for wavering in Biden’s news conference.Between the end of that presser and midday Friday, only a handful of Democratic lawmakers called on him to step aside. Others, meanwhile, declared themselves reassured. “I think he convinced a lot of people he should stay in the race,” Rep. Steve Cohen (R-TN) told CNN. Chris Coons, a Democratic senator from Biden’s home state of Delaware, declared, “Tonight President Biden was knowledgeable, engaging, and capable.”

Democrats skeptic of Biden’s candidacy suggested that his performance had set back their cause. In New York Times reporter Annie Karni’s summary of their thinking, “This may make an already very slow decision process even slower.”

But Democrats must not succumb to the gross irresponsibility of low expectations. Nothing Biden did Thursday evening indicated that sticking with him is the Democratic Party’s best bet. And Democrats have a civic duty to put forward the strongest possible candidate, given that their defeat would bring an insurrectionist back to power.

To give Biden his due, his performance Thursday night did suggest that he remains competent to perform his office’s basic functions — certainly, more competent to do so than his Republican challenger. The president demonstrated fluency in foreign affairs and an ability to intelligibly convey his thoughts, at least much of the time.

This said, the rigor and cogency of his remarks on geopolitics have been grossly exaggerated. To take just one example: At the NATO summit, Ukrainian President Volodymyr Zelenskyy pressed the United States to give his country greater latitude for using American weapons offensively. Zelenskyy argued that Ukraine could not win the war without greater freedom to strike military targets within Russia. A reporter asked Biden whether he found this argument persuasive. Here was Biden’s reply, according to the White House transcript:

We have allowed Zelenskyy to use American weapons in the near term, in the near-abroad into Russia. Whether or not he has — we should be — he should be attacked — for example, should Zelenskyy — he’s not, but if he had the capacity to strike Moscow, strike the Kremlin, would that make sense? It wouldn’t.

The question is: What’s the best use of the weaponry he has and the weaponry we’re getting to him? I’ve gotten him more HIMAR— I got him more long-range capacity as well as defensive capacity.

And so, our military is worki— I’m following the advice of my commander-in-chief — my — my — of the — the chief of staff of the military as well as the secretary of Defense and our intelligence people.

At the start of this answer, Biden struggles to articulate a coherent thought. By the end, he’s said enough to convey the broad outlines of his position to the already well-informed: He is worried about getting into a direct conflict with a nuclear superpower, so he doesn’t want Ukraine to be able to fire American weapons at major Russian cities. He thinks that he has provided Ukraine with all necessary weaponry, but he is prepared to make adjustments, should his military advisors instruct him to do so.

Of course, he did not articulate these ideas in a manner that would render them comprehensible to the typical voter. And even a more pristinely worded version of his answer would still be light on substance; Biden did not acknowledge that Ukraine has been losing ground for a long time now, nor did he explain how this trajectory could be reversed in the absence of a shift in US policy. In other words, he did not really engage with the argument he intended to rebut.

If the substance of Biden’s remarks was mediocre, the presentation was something much worse. The president sounded frail and coughed frequently. He failed to read his opening address off the teleprompter without stumbling over his words repeatedly. He referred to Vice President Kamala Harris as “Vice President Trump.” A clip of the latter gaffe rapidly amassed more than 8 million views on TikTok.

This performance did not amount to a convincing case that Democrats can best prevent Donald Trump’s election with Biden as their leader. Yet on Thursday, the president suggested that he should not need to make such a case.

Asked whether he would step down if his team presented him with polling showing that Harris would fare better against Trump, Biden replied, “No, unless they came back and said, ‘There’s no way you can win.’”

The president’s poll numbers have fallen since the debate (before which he was already on track to lose, according to the polls). But it would be an overstatement to say that he cannot possibly win. Polarization has put a hard floor under Biden’s support. If he sweeps Michigan, Pennsylvania, and Wisconsin, he will likely win reelection. He is more than 5 points behind Trump in Pennsylvania, according to RealClearPolitics’s polling average, but trailing Trump by smaller margins in the other two. It would not take an extraordinarily large polling error — or a historically unprecedented shift in political winds — for Biden to prevail.

Yet if Biden believes what he says about Donald Trump, then he should not find the fact that his odds of victory aren’t 0 percent especially reassuring.

The president is historically unpopular, and has been so for the majority of his term. His approval rating sits near 37 percent. Many voters blame him for inflation, and (mistakenly) have more faith in Trump’s ability to bring prices down. And more than 70 percent consider Biden too old to serve another term. He failed to catch up with Trump in swing states before the debate, even when the media’s attention was focused on the Republican’s felony convictions and the GOP had yet to begin seriously advertising against him. It is highly unlikely that Biden will have an easier time gaining ground, now that 1) he has repeatedly validated the electorate’s concerns about his cognitive decline, 2) the press has revealed that his team has been willfully misleading the public about his condition, and 3) his every misstatement from here until Election Day is certain to attract outsize media scrutiny.

It is possible the polls are wrong. But in both 2016 and 2020, they overestimated Democrats’ support. It is not prudent to assume that a hypothetical polling error is concealing Biden’s strength rather than overstating it.

Kamala Harris is not an ideal candidate. And she would very likely be Biden’s replacement. But she does have a lower disapproval rating than the president, and performs better than him against Trump in several recent polls. Above all, she is a competent, coherent public speaker who comes across as neither ancient nor deeply weird, a quality that favorably distinguishes her from the major parties’ current standard-bearers. I think some Democrats have forgotten what a normal presidential candidate sounds like. I’d encourage those impressed with Biden’s performance Thursday night to view it — side by side — with Harris’s remarks in North Carolina that same day:

Common sense suggests that a political party will not maximize its odds of victory by nominating a profoundly unpopular 81-year old who is trailing badly in the polls, unable to reliably speak coherently, and believed to be unfit to serve another term by the vast majority of voters. And a dispassionate read of the available data says the same. Democrats should not be satisfied with a standard-bearer who can sometimes convey the impression of bare competence when speaking publicly. And Biden should not be satisfied with retaining an outside chance of beating Trump. The Democratic Party must field the strongest possible candidate this November, so as to minimize the odds of an authoritarian insurrectionist taking power. Biden’s performance Thursday night confirmed that he is no longer that candidate.