Hillary Clinton is reportedly vetting Massachusetts Sen. Elizabeth Warren as a potential running mate, as the presumptive Democratic nominee narrows her VP short-list down to about five people ahead of the Democratic convention in Philadelphia.

The New York Times reported Wednesday that Warren, a favorite with the party’s left-wing base, had a secret meeting last week in Washington with James Hamilton, the lawyer leading the campaign’s vetting of prospective running mates.

A source close to the campaign confirmed to Fox News Tuesday that there are now about five candidates on the short-list.

Another senior Democratic source said the list includes Warren, Housing and Urban Development Secretary Julian Castro and Virginia Sen. Timothy Kaine. Additionally, House Democratic Caucus Chairman Xavier Becerra and Ohio Sen. Sherrod Brown are being considered. The source would not confirm any other potential names.

Picking Warren for her VP would be a way for Clinton to bring disenchanted Bernie Sanders supporters on board after a bruising campaign with the Vermont senator. Warren has also showed signs that she relishes a fight against presumptive Republican nominee Donald Trump, already getting into Twitter spats with the billionaire.

Democratic sources told The Associated Press that a key consideration is finding someone Clinton can work with in the White House. This boosts Kaine’s and Castro’s prospects, as well as those of Labor Secretary Tom Perez and Sen. Cory Booker of New Jersey, all of whom aides say Clinton enjoyed campaigning with.

Kaine, who was also a consideration for then-Senator Obama in 2008, brings executive experience as a former governor of Virginia and speaks fluent Spanish. Fox News is told that Kaine is a prospect as he would not overshadow Clinton and she is comfortable with him. Virginia is also a key swing state in November. Brown may be less likely as Ohio Gov. John Kasich, a Republican, would get to appoint his replacement in the Senate.

Castro is seen as a young and vibrant face who could also help seal up the Latino vote. However, the Associated Press reports that some Democrats fear he could be portrayed by Republicans as a lightweight and inexperienced.

Becerra is part of a group of House lawmakers Clinton met with Wednesday after he invited her to the caucus. Becerra has already campaigned in 10 states for Clinton and would offer some diversity to the ticket.

Clinton has been coy about where she is in terms of selecting a running mate

"I'm looking broadly and widely and I'm gonna begin to really, you know, dive into thinking hard about this," she told CBS News earlier this month. "I'm gonna be looking, first and foremost, as to who I believe could fulfill the responsibilities of being president and commander in chief."

Fox News’ Jennifer Griffin, Serafin Gomez, Mike Emanuel and The Associated Press contributed to this report.