In the emotional life of the liberal mediasphere, there was so little space between the release of the New York Times/Siena poll showing President Biden losing to Donald Trump handily across a range of swing states (doom! doom!) and the Democratic overperformance in Tuesday’s elections (sweet relief!) that one of the striking features of the polling passed with relatively little comment.

This was the remarkably strong showing for Robert F. Kennedy Jr.’s independent candidacy. When added to the swing-state polls, Kennedy claimed 24 percent of registered voters against 35 percent for Trump and 33 percent for Biden.

That number is notable along two dimensions. First, for showing Kennedy drawing close to equally from both likely nominees rather than obviously spoiling the race for one or the other. Second, for its sheer Ross Perotian magnitude, its striking-distance closeness to the major party candidates.

Yet I don’t see a lot of people entertaining the “Kennedy wins!” scenario just yet, and for good reasons: Most notable third-party candidates eventually diminish, he may be artificially inflated by his famous name, and his crankishness is so overt (whereas Perot’s was gradually revealed) that many voters currently supporting him in protest of a Biden-Trump rematch may well abandon him after a light Googling.

The world being strange, we shouldn’t take this conventional wisdom as gospel. But if we assume that Kennedy’s 24 percent is mostly about people seeking a third option rather than explicitly supporting his worldview, the immediate question is whether someone else should try to fill that space.

Someone like, say, Joe Manchin, the West Virginia senator who spiced up his announcement bowing out of a re-election bid with some talk about “traveling the country” for a movement to “mobilize the middle.”

There is already a potential vehicle for a Manchin candidacy in the No Labels movement, along with an effort to draft Manchin and Mitt Romney to run together, with Romney at the top of the ticket.

But the ideal ticket would probably lead with Manchin. For an independent run, his branding as a moderate with strong ideological differences with the left seems stronger than Romney’s branding as a conservative with strong moral differences with Trump.

When elites pine for a third-party candidate, they usually imagine someone like Michael Bloomberg, a fiscal conservative and social liberal. But the sweet spot for a third-party candidate has always been slightly left of center on economics and moderate to conservative on cultural issues — and that describes Manchin better than it does most American politicians. (It arguably described Biden once but not as he’s evolved in the past decade.)

The West Virginian could run, authentically, as an unwoke supporter of universal health care, fiscal restraint and a middle ground on guns and abortion. That’s a better basis for a run than Bloombergism or Kennedy’s courtship of the fringes, with a chance of claiming votes from Never Trumpers and the center left.

But is it worth the effort? Stipulate that Kennedy will remain in the race and hold on to some share of the vote that might otherwise be available to a third-party moderate. Then the question becomes whether both Trump and Biden could fall below their 35 and 33 percent levels in the Times/Siena poll, giving Manchin a plurality of the popular vote and a chance at an Electoral College win (because merely deadlocking the Electoral College would just send the race to the House, where — pending the results in 2024 — Trump would probably prevail).

In a polarized landscape, that kind of mutual G.O.P. and Democratic collapse seems unlikely. But if you were drawing up a scenario for it to happen, it might resemble the one we’re facing — in which one candidate seems manifestly too old for the job and the other might be tried and convicted before the general election. Such a landscape seems as if it should summon forth a responsible alternative. Confronting the American people with a Trump-Biden-Kennedy choice would be a remarkable dereliction by our political elites.

But comes the response from anxious liberals: Isn’t an even greater dereliction for a Democrat — however ornery and moderate — to embark on a run that could help re-elevate Trump to the White House?

Let’s allow that it might be, but then let’s also allow that, if current polling holds, it’s not running an alternative to Biden that seems most likely to put Trump back in the presidency.

That Trump-friendly polling may change. But it’s entirely possible to begin an independent candidacy and then suspend it (just ask Perot) if the situation looks entirely unpropitious. Which is what I’d advise Manchin to consider, if the donors and infrastructure are there: a patriotic attempt, to be abandoned if it’s going nowhere, but to be seen through if enough of the country desires a different choice.