In Sunday’s Democratic presidential debate, former vice president Joe Biden said he’d pick a woman as his running mate if he is the Democrats’ nominee. (Sen. Bernie Sanders, I-Vt., said he’s considering it but wouldn’t commit the way Biden did.)

We’ve known for some time that Biden was leaning toward a woman. He has said he’d prefer a running mate “of color and/or a different gender.” His other criteria: Someone he can trust. So, if he does win the nomination, who would be on his short list and why? Here are some educated guesses.

The short list:

Sen. Kamala Harris, D-Calif.: Yes, the former presidential candidate memorably landed a punch on Biden in one of the first Democratic presidential debates, about busing during school desegregation. But Harris is also a well-known senator and before that was attorney general of her state, and she has endorsed Biden. “She’s qualified to be president; I’d consider her for anything she’d be interested in,” Biden said in January. The potential downside to picking Harris: California isn’t really a state Biden needs to campaign much in to win a general election against President Trump.

Sen. Amy Klobuchar, D-Minn.: She’s another former 2020 candidate, who, unlike Harris, stayed in the race long enough to get votes. She came in third in the New Hampshire primaries in February. And she comes from a state that Hillary Clinton won in 2016 by only a point and a half. Also, Klobuchar dropped out of the race earlier this month and immediately endorsed Biden, contributing to the momentum that propelled him into the lead over Sanders.

Michigan Gov. Gretchen Whitmer: She’s probably the least-known name on this short list, but Whitmer is beloved by national Democrats. She won the governor’s seat in Michigan in 2018, taking it back for Democrats for the first time in nearly a decade. She delivered the 2020 Democratic address to Trump’s State of the Union. She frames herself as a moderate. And – perhaps most importantly – she is from a state that Trump narrowly won in 2016 and that will be crucial to deciding who wins in 2020.

Sen. Elizabeth Warren(D-Mass.): She and Biden don’t agree ideologically on issues such as health care, but the left took Warren’s presidential loss hard, and she could be a unifying pick for the party.

Other contenders:

Stacey Abrams: The Georgia Democrat was one of the party’s stars during the 2018 midterm election, coming close to winning Georgia’s governor mansion. She has since dedicated herself to voting rights causes and delivered one of the Democrats’ responses to Trump’s State of the Union address. She is also from a state that Democrats would like to make competitive regularly, including a Senate race in November that could be key to which party holds the majority. The potential downside: Her highest office so far has been as a state lawmaker.

Sen. Catherine Cortez Masto, D-Nev.: She is not a household name, but Cortez Masto has similar qualifications to Harris. She was Nevada’s attorney general before becoming its senator in a competitive election in 2016. She was the first Latina elected to the Senate, ever, and she is the first woman from Nevada to be a U.S. senator. Nevada is a state Democrats need to win for the White House, but it’s not as competitive as some of the other states on this list, like Michigan or Minnesota. She’s currently leading Democrats’ efforts to take back the Senate in November.

Other Democratic elected officials to watch: Govs. Gina Raimondo of Rhode Island (she is in her second term there and has held national positions for Democratic governors) and Michelle Lujan Grisham in New Mexico, who as the former chair of the Congressional Hispanic Caucus could help activate Democratic Latino voters; Sens. Tammy Duckworth, D-Ill., a war veteran with an impressive personal story, Tammy Baldwin, D-Wis., a skillful campaigner who comes from a must-win presidential state, and Kirsten Gillibrand, N.Y., another 2020 presidential contender who has championed women’s rights; and Rep. Val Demings, D-Fla., who was a House impeachment manager during the trial to remove the president.