One reason so many Democrats are running for president is that none of them is a strong enough candidate to scare off the other ones. “The Democratic field to me, so far, is more about quantity than quality,” the Cook Political Reports Dave Wasserman told the New Yorker recently.

The first televised Democratic debate, with less-than-commanding performances by Senator Sanders and Vice President Biden, triggered some Democratic fantasizing about candidates other than two dozen or so “major” candidates who are already in. Michelle Obama’s name gets mentioned a lot.

Billionaire anti-climate-change activist Tom Steyer, sensing an opening, has joined the race. Some Democrats spend time dreaming about the existing candidates but with magically altered attributes: Biden, but ten years younger. Pete Buttigieg, but ten years older, and experience as a governor rather than a mayor.

The candidate I’d like to see enter the race, though, is Senator Schumer of New York. Not that I think he’d be a particularly distinguished president; he’s too much of a big government guy for me, and he seems to me to be more of a legislative personality than an executive one.

Purely as a politician, though, Mr. Schumer outclasses any of the existing Democratic candidates. If the field limps along in its current state, Mr. Schumer may want to take a serious look at getting in.

The senator from New York could win the nomination. Certainly Mr. Schumer’s fundraising prowess would give him instant credibility. Even in the era of online small-dollar donors, the ability to raise a lot of money is still important in politics.

Mr. Schumer is already strong with three key (and sometimes overlapping) elements of the Democratic donor base — Jews, gays, and Wall Street. He’d be even stronger with a pitch to centrist Democrats that says, hey, I’m the only thing besides Donald Trump standing between you and an Elizabeth Warren or Bernie Sanders administration.

There are other candidates trying to fill that role, but they are all flawed. Mr. Biden is too old — at 76, almost precisely two presidential election cycles older than Mr. Schumer, who is 68. Senators Booker and Harris don’t quite have the gravitas.

The case for Mr. Schumer, though, isn’t just money, age, or identity politics. It has do to with the ideological landscape. There’s a difference between a “woke,” socialist Democratic Party cultivating campus activists and faculty radicals, and a Democratic Party that can still speak to middle-class, tuition-paying, working parents.

Mr. Biden can connect with those parents. If Mr. Biden is too far past his prime to succeed, though, Mr. Schumer can also fill that role with a modicum of credibility. There aren’t many others who can. How would Mr. Schumer run?

For the activist base, the senator could point to his years of advocacy for stronger gun control laws, dating back to his days as a member of the House. It made him one of the National Rifle Association’s worst enemies. He could run online ads of himself marching in New York’s gay pride parade with his daughter Alison.

For independent voters, he can run by criticizing President Trump as being too soft on China — a policy position that Mr. Schumer has been staking out anyway and that has a certain kind of Schumer-esque genius.

Mr. Schumer has more latitude than Mr. Trump to take those sorts of positions because the stock market doesn’t slump each time he clashes with China about trade.

He can use what he has in common with President Trump — long, intimate experience with New York City’s tabloid and television press, an outer-borough sensibility — to connect with voters.

Maybe Mr. Biden isn’t as over-the-hill as he seems, though it wasn’t exactly reassuring to learn that he had to refile his 2017 and 2018 tax returns in part because he, as his campaign put it, “inadvertently failed to include the W-2 income and associated withholdings from the final three weeks of the Vice Presidency.”

Maybe Mr. Schumer has concluded that Mr. Trump is a lock for a second term anyway, and that chief Democratic Senate negotiator against a Republican president is a better position to be in than losing presidential candidate.

Yet if Mr. Schumer really thinks that Mr. Trump is a threat to the republic, he owes it to the Democrats and the country to get off the sidelines and into the Democratic field. If he waits another cycle to make a run at the White House, he risks ending up like Mr. Biden — past his expiration date.