If you want to serve as the GOP's vice-presidential nominee this year, there are a few non-negotiable requirements. You need to be at least 35 years old. You need to be a natural-born U.S. citizen. And you need to be able to get along with Donald Trump — or at least, to tolerate him.

That last one may narrow the pool of available veep options just a bit. Trump is the kind of candidate who drives other, more traditional politicians crazy. He has a shoot-from-the-hip penchant for controversy, a head-spinning tendency to change his mind on policies in a moment's notice, an impressive ability to deliver colorful insults at will and a tendency to say or do things that, under the standard rules of political gravity, would doom any other candidate (like, say, getting in a fight with the pope.)

All this makes Trump's veepstakes even more intriguing than the usual veepstakes intrigue. From what we can gather, the people on Trump's short list are all traditional politicians — former House speakers, governors and senators. More than a few of them weren't Trump supporters until after he'd already become the presumptive GOP nominee.

Sure enough, count two of them out. Sen. Bob Corker (R-Tenn.) told our own Bob Costa on Wednesday he's pulling himself out of consideration for the No. 2 job, saying "it’s just not the right thing for me, and I don’t think it’s the right thing for them." And Sen. Joni Ernst (R-Iowa) strongly indicated to Politico's Burgess Everett she wouldn't take the job: "I think that President Trump will need some great assistance in the United States Senate and I can provide that." (She also said she was never being vetted to begin with.)

Trump will make his selection ahead of the Republican convention the week of July 18. Here's how some of the names on the (ever-evolving) list match up with Trump's, shall we say, more unique characteristics. (For more, see Fix founder Chris Cillizza's veep rankings.)

Newt Gingrich

The former House speaker and presidential candidate is a leading contender, according to The Washington Post's Bob Costa and Karen Tumulty. In fact, Gingrich will be campaigning with Trump Wednesday in Cincinnati. Here's how he matches up with Trump:

Anti-PC cred: Gingrich was once the face of the Republican Party. But since leaving public office in the '90s, he's become a voice that often speaks from the fringe of it. In 2012, Gingrich urged his party to accept same-sex marriage. And in 2016, while the rest of the Republican Party was hiding from Trump the best they could, Gingrich wrote an op-ed in the Washington Times praising Trump's business acumen. He's since served as a sort of informal, on-air adviser to Trump, offering up #protips like this one, which he shared with NBC recently: "Quit screwing up."

Rebound ability:  Gingrich has some of the most impressive rebound skills in Washington, a town known for second chances. Since essentially being booted from the speakership and Congress after a poorer-than-expected showing in 1998 midterm elections, Gingrich "transfigured himself from a political flameout into a thriving business conglomerate," wrote The Washington Post's Karen Tumulty and Dan Eggen in 2011. He stamped his name on various for-profit enterprises that generated close to $100 million in revenue over a decade. (Sound familiar?)

Most Trumpian media moment: Trump is no stranger to media scorn. Neither was Gingrich, particularly back in 1995 during the government shutdown, when Gingrich seemed to imply that a perceived snub from President Bill Clinton contributed to his decisions in that situation. The New York Daily News immortalized the drama with this cover:

Most nimble policy switch: In the '90s as House speaker, Gingrich helped pass NAFTA, the landmark free trade agreement between the United States, Canada and Mexico that Trump has called "the worst trade deal" in U.S. history. By last Friday, Gingrich was sounding a similar note. "I basically agree with Trump's speech on trade," Gingrich told Politico after Trump gave a speech eviscerating our nation's free trade deals.

Personal life parallel: Both men have been married three times, with their earlier divorces providing plenty of tabloid fodder. (Gingrich's first two ended in affairs, and at least one of Trump's marriages ended in a lawsuit.)

Chris Christie

The New Jersey governor was one of the first mainstream politicians to publicly back Trump, a move that shocked the political world — and drew immediate speculation Christie was pandering for a White House job after his own failed presidential campaign. Here's how Christie matches up with Trump on:

Insult skill set: This is one man who might be able to go line for line with The Donald. There are so many that NJ.com put together a Chris Christie Ultimate Insult Generator. I'm partial to this one:

Political resurrection: The 2013 Bridgegate scandal that implicated some of his top aides in closing a main thoroughfare for political retribution (a longer refresher here) wasn't pretty for Christie. He himself wasn't implicated, but his poll numbers in New Jersey plummeted and haven't really recovered. Still, he ran for president and had some pretty big debate performances before dropping out after the second nominating contest, where he came in sixth.

Most Trumpian media moment: Since you could make the case that Christie was the only candidate out there with the ability to channel Trump's approach, if not his political positions, you could make the case that his most Trumpian moment would have to be one that included Trump himself: Christie's pained expressions during a Trump news conference on Super Tuesday, a few days after shocking the political world by endorsing Trump, was Internet meme gold.

Anti-PC cred: Both men tend to deliver seemingly unfiltered opinions in a tri-state accent. And both draw a similar reaction from a majority of the voting population at large. That reaction isn't a positive one.

A March Fairleigh Dickinson University’s PublicMind poll found New Jersey voters most often used words like "bully," "arrogant" and "disappointing" to describe Christie. Meanwhile, Trump would be the least-liked major-party presidential candidate in modern history, according to Washington Post-ABC News polling.

Joni Ernst

The New York Times reported that the freshman Iowa senator, elected in 2014 as a star of the conservative movement, met with Trump on Monday and is being vetted for the running mate job. But as we noted, she all but took herself out of the running on Wednesday, and Ernst has disputed she was being vetted. Still, since we did the work, here's how she matches up with Trump on:

Most Trumpian media moment: Definitely the headline-grabbing ad in her 2014 campaign for Senate, where she defeated a Democrat in a hard-fought race for an open seat. Ernst introduced herself to Iowa voters and the world this way: "I grew up castrating hogs on an Iowa farm. So when I get to Washington, I'll know how to cut pork."

Insult skill set: It may not quite match Trump on style points, but we'd say calling the president a "dictator" and suggesting Congress should consider impeaching him is up there with the mogul's top Obama insults.

Endorsee in common: Sarah Palin. The former Alaska governor and vice-presidential candidate endorsed Ernst in her Senate race. And more recently, Palin endorsed Trump in Iowa in a speech we called "rambling, remarkable and at times hard to understand"

Endorsee NOT in common: Mitt Romney. The former Massachusetts governor not only endorsed Ernst and spent time campaigning for her in the state — his campaign alumni stocked her own team. National Journal's Andrea Drusch called Romney her "secret weapon."

It probably goes without saying, but we'll say it anyway: Romney has not been shy about his disgust for Trump. "Donald Trump is a phony, a fraud," he said in March.

Gov. Mike Pence

The former congressman and Indiana governor had some presidential buzz himself before deciding to run for a second term this fall. He'd help Trump shore up some of the evangelical vote.

Colorful skill set: Nothing from this mild-mannered Midwesterner hits any Trumpian notes. And if you had to imagine a political Twitter feed to represent the polar opposite of Trump's, it would look a lot like Pence's.

Most nimble policy switch: The religious freedom fight in 2015 that drew the ire of liberals across the nation — and landed Pence in a tough reelection battle.

After the governor spent a week taking heat for signing a law that critics slammed as sanctioning discrimination against gay people, Pence signed a revised version that didn't change the substance of the law but did make it clear it couldn't be used to discriminate against gay and lesbian shoppers, thus satisfying precisely no one on either side. #bipartisanship

Most Trumpian media moment: In 2015, the Indianapolis Star reported Pence was planning to launch a state-run news outlet that would provide pre-written news stories to local Indiana publications, break news about his administration and mix in press releases. "Just IN" was widely panned by — you guessed it — the media. A week later, Pence canceled the project.

Thing he's said that might have doomed another candidate: He's got one of those too! Although it's not terribly Trumpian. Pence (kind of, sort of) endorsed someone before his state's May primary. That someone was not Donald Trump. But that Ted Cruz endorsement — "I'm not against anybody" — was so epically lame, it immediately fed speculation he might be angling for a seat on the Trump Train.

Sure enough, Cruz ended up losing Indiana to Trump and dropping out shortly afterward. Pence promptly endorsed Trump.