Hillary Clinton met with all of the female Democrat senators Monday who happily endorsed her.

Well, almost all the female Democrat senators. One rather important Massachusetts lawmaker was missing.

Sam Frizell reports at Time:

Warren Absent From Clinton Fundraiser With Female Senators

A meeting of female Democratic senators backing Hillary Clinton’s campaign Monday had one glaring omission, but no one mentioned it. In fact, some in the room seemed to suggest that it wasn’t happening.

Thirteen of the 14 women from Congress’ upper chamber met for a fundraiser at the Hyatt Regency hotel in downtown Washington. Not joining them was Massachusetts Sen. Elizabeth Warren, who has not yet endorsed Clinton’s campaign.

But you wouldn’t have known that if you listened to the speeches.

“It’s an honor to be here with all of my Senate female colleagues,” Sen. Kirsten Gillibrand of New York said.

North Dakota Sen. Heidi Heitkamp mentioned a letter that all the Democratic women senators, including Warren, signed in 2013 urging Clinton to run…

Warren’s absence was not necessarily a slight or an indication that she won’t end up endorsing the Democratic front-runner at some point. But Warren is largely seen as the standard bearer for the party’s liberal base—who many hoped would challenge Clinton for the nomination—and withholding her endorsement is one way of lobbying the candidate to move in her direction.

Elizabeth Warren is in a tight spot. As a female Democrat, she’s expected to endorse the candidate who might become the first woman president.

On the other hand, she’s much more ideologically aligned with Bernie Sanders, who is essentially running as a stand-in for the Warren wing of the Democratic Party.

David Catanese touches on this at U.S. News and World Report:

Elizabeth Warren Only Female Senator Not To Endorse Hillary Clinton

Two months before voting begins in the 2016 presidential primaries, Sen. Elizabeth Warren remains the only female Democratic senator not to have endorsed Hillary Clinton…

Clinton now boasts endorsements from 38 of the 46 Senate Democratic members, or 83 percent of the caucus, according to The Chase, U.S. News’ political tracker.

Sen. Bernie Sanders, the Vermont independent who caucuses with Democrats, has not landed a single endorsement from a colleague. No Republican candidate has more than three Senate endorsements.

But Sanders’ campaign was eager to note that he remains in constant contact with Warren, although representatives stressed the conversations centered around Senate business, not the White House campaign.

Lots of people on the left expect Warren to eventually endorse Clinton.

What happens if she doesn’t?