The final Democratic primary underway in Washington, DC, and the city is abuzz over a tête-à-tête between Bernie Sanders and Hillary Clinton that will take place later in the afternoon. Will the Vermont senator join President Barack Obama, Senator Elizabeth Warren, and others who endorsed Clinton as the Democratic nominee this week? Will he keep his promise to fight all the way to the party's convention in July? Or will they discuss forming a unified ticket to run against Donald Trump in November's general election?
Presidential candidates usually announce their running mates in the days or weeks ahead of the national conventions, where the presidential tickets and party platforms are ratified. (Ted Cruz, who picked his nominee a week before ending his campaign this year, is a notable exception.) Clinton has yet to formally rule Sanders out as her potential VP pick, but she has joked that she would prefer Tony Goldwyn, the star of the ABC show "Scandal," over him.
Vice presidential speculation is one of America's favorite quadrennial pastimes, so we put together a list of the favorites to become Clinton's second-in-command.
The Massachusetts senator is by far the public's most popular pick for VP. Clinton faces a fierce battle against Trump, and that means getting Sanders supporters on board with her campaign will be crucial. Short of Sanders himself, Warren, a progressive darling, might be her best bet.
A member of the Senate Committee on Banking, Housing, and Urban Affairs, Warren is considered an authority when it comes to banking and regulatory issues. Like Sanders, Warren has been staunch critic of Wall Street, and she faced criticism this week when she endorsed Clinton, who has received huge paydays from firms like Goldman Sachs, which paid the presumptive Democratic nominee $675,000 to appear at three client conferences last year.
Some supporters of both Sanders and Warren have commended her for holding back her support for Clinton until nearly all of the primary votes were put away, but others aren't so sure that the office of VP would be the best posting for Warren to champion her issues.
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"Going forward, we want [Warren] to have the strongest possible role in leading the fight against political corruption and Wall St," said Charles Lenchner, a key member of the grassroots group People for Bernie. "We don't know if the strongest possible role is VP or a more senior position in the Senate. No matter how that shakes out, we'll be supporting her as one the most important progressive champions that we have right now."
Warren, who has already spent months trashing Trump on Twitter, told MSNBC's Rachel Maddow she would be ready to take on the role of running mate, if asked.
If it's true that senators are more effective in their current office than as vice president, then it may be wiser — at least for Democrats hoping to regain the Senate majority this November — to keep Booker in his New Jersey seat. But that would also be a shame because Booker would be a very complimentary choice for Clinton in a number of ways. Since the VP pick is a delicate balance between geography, demographics, age, and in 2016, probably gender, the vibrant and charismatic senator could be a vital asset for Clinton, especially in rallying the youth vote and solidifying her appeal with African-Americans.
Geographically, the New York-New Jersey duo is not ideal, but it could be countered by the senator's broad appeal and persona. Booker's Batman-esque heroics and people skills are legendary. As former mayor of Newark, he once rescued a woman from a burning house and shoveled snow from people's driveways during a wild blizzard. ("He's like a superhero with a shovel," one person tweeted.)
He's also proven himself to be a loyal Clinton comrade, stumping for her since the very first primary in Iowa. While he may not be the odds-on favorite, he could be the dark horse in the VP field.
Related: After Meeting Obama, Sanders Says He's Eager to Work With Clinton to Defeat Trump
A second-generation American born to Mexican-American parents, Castro could help boost Clinton's appeal among younger voters and Latinos in an election where immigration will be a big issue. A rising star in the party, the former San Antonio mayor was handpicked by Obama to serve as secretary of the Department of Housing and Urban Development. He hasn't made any waves — either positive or negative — after holding the position for two years, but his connection to Texas could help Clinton secure more votes in the South.
To some, Tim Kaine is the Judge Merrick Garland of VP picks: A moderate, an uncontroversial white male who could potentially appeal to Republican sensibilities. In other words, he's the safe choice. As chairman of the Democratic National Committee from 2009 to 2011, Kaine kept an amazingly controversial-free profile, which seems like a feat when compared to what current DNC chairwoman Debbie Wasserman-Schultz has faced in recent months. It's also given him an edge in terms of fundraising expertise and keeping donors and party members happy.
A Virginia senator and ex-governor of the state, Kaine also speaks fluent Spanish, which he picked up while serving as a Catholic missionary in Honduras. He once delivered a pro-immigration speech on the senate floor entirely in Spanish, and while it's not safe to assume that a Spanish-speaking white man will appeal broadly to the Latino vote, it can't hurt either.
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Follow Liz Fields on Twitter: @lianzifields