If Warren aligns herself with Clinton, she may hurt her credibility with progressives. Fans of the senator love her because they view her as uncompromising. Warren has cultivated her political persona in part by not hesitating to publicly challenge the Obama administration over issues such as corporate accountability and international trade. It would be difficult for Warren to speak out against a Clinton administration as VP. Some progressive voters might see the decision as an unforgivable compromise. “I think she would be giving up a lot more than she gains,” said Brad Bannon, a Democratic strategist and president of Bannon Communications Research. “She wouldn’t have the same visibility. It might be a move up in the organizational charts, but it would be a move down in influence.”

Congressional Democrats could find themselves at a disadvantage, too. If Massachusetts’s Republican governor, Charlie Baker, were to temporarily appoint a replacement to Warren’s current seat, that could pose a challenge for Democrats as they try to win back the Senate majority. The Boston Globe reported on Friday that “Senate Democrats may have found an avenue to block or at least narrow ... Baker’s ability to name a temporary replacement.” Even so, Warren as VP would add another layer of uncertainty to November’s highly anticipated elections.

Of course, if Warren becomes Clinton’s VP, there are plenty of ways that could help Democrats. A woman presidential candidate joined by a woman vice-presidential candidate would make an already historic ticket even more noteworthy, as David Graham points out. That might energize Democratic voters and increase turnout, which could help Democrats win the White House and benefit candidates running in races lower on the ballot.

Democratic power brokers seem to think Warren could make a good VP. House Minority Leader Nancy Pelosi called the possibility of a woman vice president “fabulous” in an interview on Tuesday, in which she also endorsed Clinton. “We’ve had two men over and over again for hundreds of years,” Pelosi told ABC. “I think that two women—whoever they may be—that would be fabulous as well, but Hillary Clinton will choose the person that she feels most comfortable with.”

Even if Warren traded in the visibility she has in the Senate by becoming vice president, she could still end up with more political clout. As vice president, Warren would be more proximate to power than she is currently. Warren has long worked within an institutional power structure, from the Treasury Department to the Senate, and still found ways to exert her will while maintaining progressive credibility. Ryan Grim of The Huffington Post points out that Warren managed to wield power from inside a Democratic presidential administration when she helped set up the Consumer Financial Protection Bureau, as well as from the Senate, despite hand-wringing from “friendly skeptics” who worried she would lose her independence. As VP, Warren could conceivably build on that track record to leave a lasting mark on policy.