NEW YORK — Mayor Bill de Blasio — not particularly popular, not particularly pleasant, not particularly accomplished — announced his presidential candidacy the other day. Nobody was excited, but then again nobody was surprised. After all, everybody else is running for president. Why shouldn’t he?

Or so it seems. About two dozen Democrats are in the field now, some even more implausible than New York’s embattled and often belittled chief executive. De Blasio is the second political figure from the Empire State to join the race, but there are so many in this contest that there actually are multiple candidates from three other states: Texas, Massachusetts and California. Indeed, there are as many candidates from these four states alone as there were in the entire field in the Democratic contest in 2008.

Here in New York, where Sen. Kirsten Gillibrand also is a contestant, Democrats are beginning to worry that a field rich in candidates could swiftly be a field poor in prospects. That, of course, did not apply to New York’s other figure in the 2020 presidential election, but then again no simple, reasonable or predictable calculus applies to Donald J. Trump, who — improbably but not inevitably — emerged from a field of 17 to win the Republican nomination and then the White House.

That 2016 GOP crowd feels quaintly diminutive in comparison to the Democrats, now one short of the composition of the Yankees’ regular-season roster. The question isn’t whether this is a field of dreams. It isn’t, not when the youngest of the two top competitors is 76 years old, when one of them dropped out of a previous race because of two plagiarism charges, and when the other cozied up to the Sandinistas and visited Managua while official U.S. policy was to oppose Daniel Ortega and his leftist government.

No, the question is: Does the party have a cleanup hitter?

Not yet, though former Vice President Joseph R. Biden Jr. seems to be swinging for the fences. But this is a long campaign, and Biden is particularly prone to season-ending injuries. (He’s had two.) Meanwhile, the big field has changed the dynamics of the presidential campaign.

In conventional campaigns, candidates seek to display mastery of a broad spectrum of issues, the better to show their suitability for the Oval Office. That’s why former Vice President Walter F. Mondale, a stalwart of Democratic social-issue reform, spent months studying the Federal Reserve Bank before running for president in 1984 and why Rep. Jack Kemp of New York, known for his involvement in conservative economic issues, boned up on foreign policy before joining the Republican field four years later.

In this campaign, candidates are seeking discrete areas of emphasis.

In conventional campaigns, Rep. Tulsi Gabbard of Hawaii (avoid foreign wars), Sen. Elizabeth Warren of Massachusetts (wealth tax), Gov. Jay Inslee of Washington (climate change), Rep. Seth Moulton (national service), Sen. Amy Klobuchar (infrastructure and the opioid fight), Sen. Kamala Harris (gender pay gap) and Gillibrand (women’s issues) might be dismissed as single-issue candidates, the way two anti-abortion candidates (the Democrat Ellen McCormack in 1976, the Republican Gary Bauer in 2000) were. Not this time.

In this campaign, that profile might assure them at least a small slice of support in a contest where a small slice of support might be enough to separate them from the crowd, which is to say candidates with almost no support. Here de Blasio — three-quarters of his constituents here, according to a Quinnipiac poll, think he shouldn’t do this — and Mayor Wayne Messam of Miramar, Florida, come to mind, along with Rep. Tim Ryan of Ohio. I could go on. Indeed the mystery is why some of them do go on.

“There’s a bunch of these candidates who have no plausible path to the nomination,” says L. Sandy Maisel, a Colby College political scientist. “Unless they get out, the winner of Iowa or New Hampshire could have about 20% or 25% of the vote. That’s a terrible situation for the party — and for democracy.”

But there is no mechanism to force those 18 or so certain losers from the race. The days are over when party bosses controlled the nominating process, and, considering their record overall — William McKinley, Warren G. Harding — maybe that’s not such a bad thing.

Besides, the chairman of the Democratic National Committee, former Labor Secretary Tom Perez, is possessed of a gold-plated resume, a pleasant smile and no influence whatsoever. Nobody in Washington or anywhere else refers to him as Boss Perez, though it might be better once in a while if someone did. He has no more chance of muscling a few of these inconsequential candidates out of the race than does Bruno Sammartino, for 11 years the WWF world heavyweight champ. Sammartino died 13 months ago.

It is enough for Democrats to yearn for a smoke-filled room, even in an era when smoking is viewed as slightly disreputable and highly unhealthy. What the Democrats need is for someone to sidle up to some of these people and say: You’re wasting your time and ours, go back home or to the House and let us have a chance of winning the election.

Then again, that is what the Democrats pretty much said in the last election — the party was so invested in Hillary Rodham Clinton that it was severely criticized for it — and look how that turned out. And had there been a GOP smoke-filled room, what do you suppose the chances would have been for someone to tell the maven from Manhattan that he had no business clogging up a perfectly reasonable process by thinking he could be elected president?

All this is the result of the democratizing of the process, which overall is a good thing for the public — except maybe in political years, when almost everyone in one party wants to be president even as everybody in that same political party agrees that the main thing is to defeat the incumbent president.

Ordinarily, political parties around this time of the year begin to think about a process called get-out-the-vote. That’s surely going on, for Iowa and New Hampshire are thick with political activists gearing up for that effort. But maybe what the Democrats really need is half that message, directed at three-quarters of their candidates: Get out.