On Wednesday night, Julián Castro will stand between Cory Booker and Tim Ryan at Miami’s Adrienne Arsht Center for the first Democratic presidential debate of the 2020 campaign cycle.

I’ll be paying special attention, however, to the former San Antonio mayor’s interactions with the candidate to Booker’s immediate left, Elizabeth Warren, for any subtle, borderline-imperceptible hints on how they vibe together.

Warren, the two-term Massachusetts senator and progressive hero, is surging in the polls right now. A Monmouth University poll of national Democratic voters, conducted from June 12-17, found Warren in second place, behind former Vice President Joe Biden, at 15 percent. That represents a nine-point jump since April, easily the biggest growth spurt for any Democratic candidate.

At a time when Biden finds himself answering for a wide range of controversial statements and legislative actions over the course of his half-century political career, Warren is positioning herself as the party’s most credible anti-Biden: someone who shares Vermont Sen. Bernie Sanders’ critiques of the way our economic system breeds extreme opportunity disparities, but brings more texture to the argument.

Unlike Sanders, she doesn’t hesitate to call herself a capitalist. She simply believes that when capitalism gets corrupted by powerful interests, the government needs to step in and redress the imbalance.

Warren is important to Castro for reasons that go beyond the mutual admiration society they’ve recently formed.

Last month, Warren praised Castro’s “People First” immigration plan during an interview with MSNBC host Lawrence O’Donnell. She followed up the interview by tweeting, “I admire (Castro’s) smart ideas on reforming our immigration laws. We should all pay attention to them.”

Castro responded in kind, tweeting, “Thanks for the shout out, @ewarren. You’re setting the pace on policy.”

It’s not an insult to Castro’s earnest presidential campaign to say that his best prospect during the 2020 election cycle is the VP slot on the party’s national ticket. And his best bet to get that nod would come from Warren, for reasons that involve the inevitably crass calculus of identity politics.

If any of the Democrats’ top male contenders — such as Biden, Sanders and Pete Buttigieg — get the presidential nomination, they will give extra consideration, when it comes to picking a running mate, to female candidates.

It’ll be a natural reaction to the growing power of women in Democratic politics, which manifested itself in a 2018 midterm that resulted in a record 106 Democratic women in Congress. It’ll also be an acknowledgment of the power of the #MeToo movement — and the corresponding national exasperation with the way white men have dominated our politics.

Most likely, Castro would only get serious consideration for the VP position if a woman wins the Democratic presidential nomination. At the moment, Warren seems to have the best chance of making that a reality.

If we accept the idea that presidential nominees want a running mate who’ll balance the ticket, Castro would provide balance in almost every conceivable way: region, gender, age (Warren will be 71 on election day in 2020, while Castro will be 46) and ethnicity.

Contrary to the suspicions of his detractors, Castro didn’t enter the 2020 presidential scrum as a way of angling for a VP offer. In fact, the reason he decided to run for president is that he didn’t like being in the passive role of waiting three years ago for that phone call from Hillary Clinton.

Nonetheless, Castro’s presidential campaign has made him a substantially stronger running-mate option this time around than he would have been for Clinton. In a sense, he’s been vetted by the campaign trail, demonstrating an ability to think on the fly, communicate with town-hall audiences in various parts of the country and roll out serious policy initiatives.

He looks and sounds like a real presidential candidate, something that wouldn’t have been obvious until he put himself out there as a candidate.

The virtues of his candidacy, however, haven’t translated to the polls, where he’s mired in the bottom tier of candidates, around 1 percent in most national polls. In the latest University of Texas/Texas Tribune poll, he was tied for seventh in his home state, with only 3 percent support.

He would be ideal for Warren, however, because he would be a loyal, articulate salesman for the ticket who wouldn’t overshadow the presidential nominee. He also would add a degree of subject-matter expertise on some key issues: immigration, housing and pre-kindergarten education.

If it’s possible to run for president and audition for vice president at the same time, that’s what Castro will be doing on Wednesday night.

@gilgamesh470

Gilbert Garcia is a columnist covering the San Antonio and Bexar County area. Read him on our free site, mySA.com, and on our subscriber site, ExpressNews.com. | ggarcia@express-news.net | Twitter: @gilgamesh470