Clinton picked Timothy Kaine for VP. Here’s who she passed up.

Clinton’s pick could fire up wary liberal voters.

Clinton withstood a tougher-than-expected primary challenge from Sen. Bernie Sanders of Vermont. A would-be vice president from the more liberal wing of the party could do wonders to bring along that bloc of voters that isn’t quite ready for Clinton. Someone with a populist message could also serve Clinton well in the attack-dog role against Trump.

Clinton would probably prefer to choose someone not named Elizabeth Warren or Bernie Sanders. Another liberal who might appease the Sanders crowd: Largely unknown Labor Secretary Thomas Perez.

[ Hillary Clinton isn’t picking Elizabeth Warren for vice president. Here’s why.]

Clinton’s pick could emphasize her history-making candidacy.

Clinton, the first woman to top a major-party ticket, could play up her barrier-breaking candidacy by choosing another woman, or a minority, to complete the Democratic ticket.

The obvious choice, and the one getting the most buzz, is Secretary of Housing and Urban Development Julián Castro. In terms of Hispanic appeal, Rep. Xavier Becerra would also make sense, but his home state of California is pretty much in the bag for Clinton already. Clinton’s campaign manager has said that a woman will be on their shortlist. Adding to the intrigue: The Boston Globe reported that Senate Minority Leader Harry Reid has been exploring options should a Senate vacancy arise in Massachusetts. Sens. Amy Klobuchar and Jeanne Shaheen could be other female options.

[ How Hillary Clinton turned a losing 2008 campaign into a winning 2016 one]

Clinton’s pick could also be influenced by geographic concerns.

Trump claims he can turn traditionally blue Midwestern states red; a VP from that region could help Clinton shore up support there. It’s unclear whether a vice presidential pick from a swing state would help deliver that state’s electoral votes in November, but the possibility of that happening could factor into the decision.

Clinton would appear unlikely to pick a fellow New Yorker as her VP pick, as the Constitution says two candidates cannot win the electoral votes from a state they both reside in. However, one of the candidates could establish residency in another state, which has happened before; then-Texas resident Dick Cheney did so when he was then-Texas Gov. George W. Bush’s VP pick in 2000.

For swing-state appeal, Clinton could choose either of the senators from Virginia, Timothy M. Kaine or Mark R. Warner, though she will probably stay away from Gov. Terry McAuliffe. Sen. Sherrod Brown of Ohio would be another obvious swing-state choice with populist appeal.