Presumptive Democratic nominee Hillary Clinton has recently campaign with Massachusetts Sen. Elizabeth Warren, a progressive, anti-Wall Street icon who could appeal to the party's left wing and draw Bernie Sanders supporters to Clinton's side.
"I'm here today because I'm with her," Warren said at a Cincinnati event in June, endorsing Clinton after a long silence during the Democratic primary race.
Warren, the former Harvard professor who set up the Consumer Financial Protection Bureau, has also served as an effective attack dog against rival Donald Trump in recent weeks, calling him a selfish "money grubber" who "will crush you into the dirt to get whatever he wants." He, in turn, often refers to her as "Pocahontas," a reference to Warren's unproven claim that she is part Native American.
Credit: REUTERS/Aaron Josefczyk
New Jersey Sen. Cory Booker
New Jersey Sen. Cory Booker is no longer denying that he's being vetted as a possible Clinton running mate.
"I'm just referring questions about the vice presidency to the woman who is going to have to make this decision," the former Newark mayor said on CNN in July. "You should talk to the Clinton campaign. What I do know is that on the Democratic side, there are many fabulous candidates--people that could be really strong vice presidential candidates."
But there's one downside of Booker as VP -- his Senate replacement would be chosen by New Jersey's Republican governor, Chris Christie.
Credit: DOMINICK REUTER/AFP/Getty Images
Colorado Gov. John Hickenlooper
Clinton "briefly" spoke with Colorado Gov. John Hickenlooper about the VP job, according to an interview the governor gave with Bloomberg TV.
When the governor was asked whether he would join Clinton on the ticket if asked, he said: "Oh sure. I think, especially if you look at the challenges that this country and the world faces right now, if you're someone who's asked, that you're one of the people that can really make a difference and your country needs you, of course you take it seriously."
He met with Clinton last week, when she met with top contenders for the running mate position at her D.C. home.
Credit: Alex Wong, Getty Images
Virginia Sen. Tim Kaine
Tim Kaine has served as Virginia's governor, chairman of the Democratic National Committee, and he's now a U.S. senator. For Clinton, Kaine would be a traditional choice: "Boring," as Kaine admitted in an interview with NBC News in June. He's also been a missionary (he speaks fluent Spanish) and is a devout Catholic.
He's a staunch supporter of Clinton as well, adding in that interview: "I have got one job and one job only right now, and that is to work hard for Hillary Clinton."
Credit: Drew Angerer, Getty Images
Labor Secretary Tom Perez
Labor Secretary Thomas Perez has given an increasing number of media interviews since Clinton has taken on the mantle of presumptive Democratic nominee.
Perez, a Hispanic lawyer with a background in civil rights, has become both an attack dog against Donald Trump and a surrogate for Clinton, calling Trump a "train wreck" and an "outsourcer in chief."
Of Clinton, in a recent NBC News interview, he said: "What I have seen working with Secretary Clinton is she is a steady hand."
Credit: Alex Wong/Getty Images
Ohio Sen. Sherrod Brown
Ohio Sen. Sherrod Brown, a popular Democrat in a crucial general election swing state, is another possible name on Clinton's VP short list.
His appeal to white, blue-collar voters -- a demographic Clinton struggles with in public opinion polls -- could also help win over supporters from Bernie Sanders' side.
Credit: Andrew Harnik, AP
Agriculture Secretary Tom Vilsack
Secretary of Argiculture Tom Vilsack is also in the running for Clinton's No. 2 slot.
The former Iowa governor spoke with the Associated Press ahead of the Democratic convention about his annoyance with Trump's catchphrase.
"I get really irritated when I hear Donald Trump say, 'Let's make America great again,'" Vilsack said in the interview. "I look at it and I think, wait a second, I started out life in an orphanage. I didn't have a last name. ... America gave me this opportunity to go from that beginning to sitting in the White House in the Cabinet Room with the president of the United States."
Vilsack, back when he was Iowa's governor, endorsed Clinton for president in 2007.