Twenty-four people are hoping to win the Democratic nomination in the 2020 presidential election. (Reuters)

Now that New York Mayor Bill de Blasio has entered the 2020 Democratic primary, we think the field is set. (Okay, Georgia politician Stacey Abrams could decide as late as the fall, but that’s the only question mark we know about.)

That means at least two dozen people are seriously competing in the primary. With each new entrant, I’ve been asking myself: What would it take for this person to win the nomination? In some cases (with, say, Biden or Sanders), it’s pretty clear. That question becomes much more difficult, though, when we’re talking about the likes of some little-known House member.

So just for fun, I thought I’d make a brief case for how each major candidate could win. To clarify, this is a highly unscientific exercise. I make no predictions and pick no front-runners. If you disagree or think you have a better idea, let me know in the comments or email me.

Former vice president Joe Biden: Democrats decide that what matters is unseating Trump, and Biden runs a much better campaign than he has before. A recent Quinnipiac University poll showed 38 percent of Democratic voters said they supported Biden, but 56 percent said he would have the best chance against Trump. That could be a function of his former office and his well-known name, rather than some calculation about his appeal to Midwestern/Rust Belt voters, etc. Keep an eye on whether people continue to see him as the most electable as other candidates become better known.

Sen. Bernie Sanders (I-Vt.): Biden falters, Sanders prevents Sen. Elizabeth Warren from eating into his base, and Democrats decide they don’t need to compromise to defeat Trump. Oh, and Sanders somehow figures out a way to appeal to nonwhite voters, whom he struggled mightily to win in 2016.

Sen. Elizabeth Warren (Mass.): Sanders doesn’t run a strong race, and Democratic voters decide they want someone with real liberal bona fides and the most detailed policy proposals. They also decide that they want to tempt fate by nominating another candidate from Massachusetts.

Sen. Kamala D. Harris (Calif.): She convinces voters that she’s got the most inspiring candidacy and she’s the kind of former prosecutor who could go toe-to-toe with Trump on the debate stage — and win. It also wouldn’t hurt if California moving to near the front of the primary process can give her a nudge, given all the delegates it has.

South Bend, Ind., Mayor Pete Buttigieg: Biden falters, and Democrats want to compromise between someone with potential Midwestern appeal and who excites the base. He also convinces people that a person who would be the youngest president to ever hold office wouldn’t be outmatched by Trump.

Former congressman Beto O’Rourke (Tex.): He figures out exactly what his campaign is about and recaptures some of the magic of his underdog 2018 campaign against Sen. Ted Cruz. (It’s one thing to run strong against a polarizing figure like Cruz; it’s another to beat out a bunch of fellow Democrats.)

Sen. Cory Booker (N.J.): The senator is able to beat out other candidates in the field for black voters (Harris), young voters (Sanders) and moderate/pro-business voters (Biden) — or assemble enough of a coalition in those demographics to be something of a consensus candidate.

Sen. Amy Klobuchar (Minn.): Democrats decide they want something about as far from Trump as possible — a moderate, understated Midwestern woman who will offend almost nobody and has won her previous campaigns handily.

Sen. Kirsten Gillibrand (N.Y.): She somehow overcomes an extremely tepid start to get on the debate stage and shows she has some real conviction about liberal causes — despite her past as a more moderate Upstate New York congresswoman.

Washington Gov. Jay Inslee: Democratic voters decide that climate change is the existential and immediate crisis that the Washington governor and others say it is and want the candidate most focused on that issue. They are also looking for someone with experience as a governor (which is actually pretty rare in this field).

Former Colorado governor John Hickenlooper: The governor thing, except they want someone who has also been successful as a businessman and speaks to those issues. (And they can overlook the whole “Deep Throat” thing.)

Montana Gov. Steve Bullock: They like the idea of a governor, and they want someone who was won in a conservative electorate. In fact, Bullock is the only candidate in this field to win statewide in a red state in recent history.

Sen. Michael F. Bennet (Colo.): The understated senator runs a slow-and-steady campaign while the other candidates fight among themselves, and he shoots the moon at the right time with his message about economic mobility.

Former housing and urban development secretary Julián Castro: If Latino voters unite behind him in key early states like Nevada and California, and if he can take advantage. Hispanics were 19 percent of the Nevada caucus vote in 2016 — and could be a much greater percentage in a 29 percent Hispanic state — and 30 percent of California’s vote in 2008, the last year for which exit polls are available in that state’s Democratic primary. Castro is the only Latino candidate in the 2020 Democratic field. He’s also the only one with experience as a Cabinet official.

New York Mayor Bill de Blasio: The mayor pulls off the greatest image recovery since Trump. A recent Quinnipiac University poll showed just 14 percent of Democratic voters view him favorably, vs. 35 percent who view him unfavorably — 21 points underwater in his own party. (Around the time Trump entered the 2016 GOP primary, his numbers among Republicans were 42 points underwater.)

Rep. Tulsi Gabbard (Hawaii): The party wants a nominee with a completely unique foreign policy — including on Russia — that has often irked the party establishment.

Former congressman John Delaney (Md.): The party wants the most successful and richest businessman in the field and decides it wants a pragmatic, moderate, pro-business candidate.

Rep. Tim Ryan (Ohio): People who were pining for Sen. Sherrod Brown (D-Ohio) to run line up behind another Ohio Democrat trying to offer a similar message. Oh, and the “yoga vote” turns out strong.

Rep. Eric Swalwell (Calif.): Newly empowered House Democrats uncover more about Russian interference in the 2016 election, and the House Intelligence Committee member can seize the moment.

Rep. Seth Moulton (Mass.): The congressman, who has pushed for House Speaker Nancy Pelosi to step aside, convinces Democrats that they need to hand things off to the next generation and that he is the one to lead the transition. Oh, and the Massachusetts thing.

Business executive Andrew Yang: He harnesses the power of the Internet like we’ve never seen before in presidential politics.

Author Marianne Williamson: She gets enough attention that people start reading her four books that reached No. 1 on the New York Times’s bestseller list and fall in love with her message about spirituality.

Miramar, Fla., Mayor Wayne Messam: They like Buttigieg, but want someone who was the mayor of a slightly bigger city. And they like Booker, but they want someone who was better as a Division I college football player.

Former senator Mike Gravel (Alaska): Something really crazy happens because even the former U.S. senator said he wasn’t trying to win — before changing his tune.