Hillary Clinton’s choice for a running mate has entered a new and more intense phase, according to Julie Pace and Lisa Lerer of the AP, who say Elizabeth Warren, Tim Kaine, and Julián Castro have been asked for "for reams of personal information" and are scheduling interviews with Clinton’s vetting team.

The case for and against Warren has been well-covered in the media, and Kaine seems like a safe, unremarkable pick. Castro is not ideologically controversial in the same way that Warren is, but would nonetheless be a choice with more upsides and downsides than Kaine. He’s been marked as a rising star in Democratic Party circles for years, underscored by his selection as a keynote speaker at the 2012 Democratic Convention when he was a young, fairly obscure San Antonio mayor.

Were Texas not such a rock-ribbed conservative state, the next logical move would have been a run for statewide office. Were his twin brother not already occupying the House district that contains his San Antonio base, a career in Congress could have been a fallback.

But neither of those were options, which left a Cabinet gig as his best chance to move up. And so when the post of Housing and Urban Development secretary opened and the Obama administration offered it to him he gladly accepted. The move to Washington only increased the buzz around Castro, and things like his speechwriter going to work for the Clinton campaign further intensify it.

And Castro really does seem like he’d do the job of vice president — attack dog on the stump, glad-hander in office — very well. But the questions about Castro center on the "maybe the president will die and then he’ll be president" aspects of the job rather than the day-to-day work of vice presidenting.

Who is this guy?

Julián Castro’s mother, Rosie Castro, was a Chicana activist in the city of San Antonio who was involved in the founding of the short-lived Raza Unida party. The party had support throughout the Mexican-American communities of the Southwestern United States and saw its greatest institutional success in the heavily Latino Rio Grande Valley areas of Texas before fizzing out amidst the general decline of radical politics in the late 1970s and growing Democratic Party courtship of the Hispanic vote.

Castro and his twin brother Joaquin (who is now a Congress member) were born in 1974, and Julián has recounted that his mother’s continued political activism was an enormous influence on his decision to enter politics.

Julián and Joaquin both attended Stanford in the early 1990s, both graduated from Harvard Law School in 2000, both took jobs at Akin Gump Strauss Hauer & Feld after graduation, and left together to form their own law firm in 2005.

They also both made the relatively unusual decision to follow up their elite legal education by moving back to San Antonio rather than a bigger commercial center. In 2001, Julián won election to a city council seat, and the following year Joaquin won a seat in the state legislature. In 2009, Julián won election as mayor — a relatively weak office in a city with a council-manager system — and in 2012 Joaquin won a seat in Congress.

San Antonio is a heavily Latino, safely Democratic city located in the very conservative state of Texas. Both Castros chose to hew close to the national party mainstream, in ideological terms, rather than try to tack right to win statewide office. This left Julián’s path to upward mobility after the mayorship unclear, and he accepted an offer to become HUD secretary in 2014.

The pros of vice presidential nominee Julián Castro

Castro would bring a lot of useful thematic and demographic balance to the Democratic ticket — a young Hispanic man to complement an older white woman.

Clinton, Castro, and Obama would in many ways form a perfect three-headed dragon to attack Donald Trump, represent the modern Democratic Party, and advance a policy agenda that’s distinctly progressive without adding any ideological innovations that would alarm Trump-skeptical white college graduates.

Castro also has a good eye for skating where the puck is going, politically speaking, and staying in the ideological mainstream of Democratic Party politics. This is a little boring, but it’s very vice presidential and also reflects Clinton’s own approach. His signature initiative as San Antonio’s mayor was starting a preschool program, and under his leadership the city also launched a bicycle sharing system that, though wildly inappropriate to the city’s actual urban form, put him in line with a fashionable cause in coastal urbanism.

At HUD he’s focused on combatting racial discrimination and combatting smoking, two more initiatives that put him firmly in the center of the Democratic Party consensus.

The cons of vice presidential nominee Julián Castro

Well, he’s the secretary of Housing and Urban development and the former mayor of San Antonio — and that’s it.

Clinton does not particularly need to add gravitas or experience to her ticket, but she does need to be able to say with a straight face that her VP is well-qualified to take over in the Oval Office in the event of her death and incapacitation. Dan Quayle served four years in the US House of Representatives and eight years in the US Senate and was still considered a bit of a lightweight VP choice for George H. W. Bush.

Former HUD Secretary Jack Kemp was Bob Dole’s VP pick in 1996, but Kemp had 18 years of experience in the House under his belt, during which time he emerged as a major factional leader. Castro isn’t just young, his nose for the ideological sweet spot means he hasn’t really distinguished himself in any particular way.

Last but by no means least, Castro hasn’t used his time in Washington to particularly wow anyone with his grasp of policy. Even though he’s in a second-tier cabinet post, he’s not an obscure figure. You could imagine a world in which journalists’ Castro profiles were full of lines about how his resume’s not great but if you talk to the guy for 30 minutes you’ll come away so impressed with his intelligence and integrity that you hope his inexperience will be overlooked. It hasn’t really happened so far, and he’s arguably running out of time to make it happen.

Castro also gets needled for his apparently poor command of the Spanish language, a reflection of the fact that his family’s roots in San Antonio date back to 1920. As someone who does not speak Spanish and whose family also immigrated to the United States from Latin America in the 1920s, I don’t personally find this odd. But there is certainly a sense that a Spanish-speaker could be a more effective campaigner among Hispanic voters.

The bottom line

Vice presidents have often been selected with an eye toward complementing the existing strengths of the presidential candidate.

Clinton’s resume is more extensive and impressive than that of any president since the founding generation, so in that sense she might be able to get away with a running mate whose resume is unusually thin. Barack Obama and George W. Bush had very thin resumes, so they picked older VPs with much more extensive experience. Clinton could be tempted by a younger VP with much less experience. And Castro’s experience is concentrated in the one main area of American public policy — municipal government — where Clinton has never worked.

He’s also a candidate who’s mostly done things liberals like, but who the business community doesn’t have any particular problem with — an asset as Clinton tries to assemble a landslide coalition rather than a minimum winning one. He’s good at speeches, he’s reasonably charismatic, and he could help Clinton build bridges with younger voters while pressing the attack against Trump on the stump.

But could he be president? By putting him forward, Clinton would be asking America to trust her judgment on a person who is not qualified by conventional standards. A sense that Sarah Palin — an actual governor of a state, albeit a small and weird one — wasn’t up to the job seems to have hurt John McCain badly in 2008.

And Castro not only lacks experience at the highest levels of government, he lacks the kind of experience with national media appearances that would ensure he’ll be able to put doubts about his experience to rest.

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