On Tuesday, the Associated Press reported that, according to Democratic insiders, three of the politicians on Hillary Clinton's vice presidential shortlist were: Sen. Elizabeth Warren of Massachusetts, Sen. Tim Kaine of Virginia, and Housing and Urban Development Secretary Julián Castro of Texas. The Associated Press report did not indicate whether the shortlist included other potential contenders, but it did note that her Democratic nominee rival, Bernie Sanders, was not a possibility, according to one Democrat.
Each of these three potential vice presidential picks offer clear advantages to Clinton's campaign, though also come with potential drawbacks. Warren has, arguably, already earned the most buzz as a possible running mate for Clinton. She's a favorite among progressives, and she's only risen in their esteem as one of the most outspoken critics of Donald Trump. However, many, including Clinton, have wondered whether the United States is ready to see two women head a party on the general election ticket. An even bigger concern may be related to Clinton's Wall Street donors; according to a report in POLITICO, some major Democratic donors in the financial sphere do not want Warren, who has vehemently attacked Wall Street policies, as Clinton's running mate.
Kaine is far more moderate than Warren. If Clinton taps him to be her VP, it will certainly be seen as a play for independent voters, which could potentially turn off Sanders' supporters. However, Kaine is well liked among Democrats and was seriously vetted by Barack Obama in 2008, ultimately just finishing runner up to Joe Biden. A Democratic official who had worked with Kaine spoke favorably of him to POLITICO, but said he may lack the ferocity to attack Trump (the way Warren does):
What he's not is an attack dog. He never enjoyed that part of the gig as chair of the party. It's not his natural disposition. He's a thoughtful guy who likes to play in the world of facts and policy. He doesn't shoot from the hip, and he's not a sound-bite master.
Castro is the youngest of this trio — and has the least political experience. Castro, 41, served as mayor of San Antonio for five years before Obama nominated him for Secretary of Urban Housing and Development. While Castro may have been being modest, as recently as May he dismissed the possibility of being Clinton's vice presidential pick. When asked about it on CNN, he simply said, "That's not going to happen."