Who's on Donald Trump's Veep List?

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The job description: A person who has familiarity with Washington and can help the presumptive Republican nominee achieve his legislative agenda on Capitol Hill while inspiring confidence abroad.

The requirements: Some government experience, but not necessarily elected office. National security expertise and/or military service is strongly encouraged. Must have a high tolerance for unpredictability and controversy, and exhibit grace under fire.

The start date: July 18, 2016, the beginning of the Republican National Convention, with the potential to continue until January 2025.

The position: Running mate and possible vice president of the U.S.

Donald Trump has said he has five to seven names in mind as possibilities to fill out the top of the GOP ticket this year, a decision he plans to reveal in Cleveland two months from now. But those close to him tell U.S. News that even his own list is a fluid one depending on the day, a new bit of information he's come across or whom he's talking to.

One adviser, who requested anonymity to speak candidly about the process, says Trump recently expressed exasperation about his options. "He's very dissatisfied with all of his choices," the adviser says. "There are people on the list that aren't going to be vice president."

That is part of the parlor game, of course: separating whom to float for mere media consumption (there must be a woman) from whom to screen and probe thoroughly for the second-highest office in the land.

There's also the spiteful part of Trump to consider: Former Arizona Gov. Jan Brewer received a compliment because she was for him during the primaries. South Carolina Gov. Nikki Haley, who was against him, got dissed.

The choice of a running mate is one of the most closely guarded secrets inside a presidential campaign, because its revelation marks one of just a few instances in which a candidate can largely command a modern news cycle without much distraction or distortion. And more than most, Trump understands the potency behind the big reveal.

"Keep a little suspense at least, right?" Trump quipped to Fox News' Greta Van Susteren recently in declining to list names.

The Trump campaign says they're still in the infancy of the vetting process and the candidate himself has spent recent days disputing names that have been floated in media reports as being under consideration, such as Sen. Marco Rubio of Florida.

"It's not based on the same criteria as used in the past," says Trump campaign manager Corey Lewandowksi, who is shepherding the selection process. "Geographic representation is out the window. The main criteria of the vice president is being capable of running the government, agnostic of gender and all other considerations."

Given Trump's unorthodox candidacy, the pick holds even more magnitude because of the significant number of Republicans who remain skeptical of his seriousness and gravitas as a potential commander-in-chief.

At this early stage, the campaign is signaling that Trump is more inclined to enlist a governing partner – a la Barack Obama's choice of Joe Biden in 2008 – than someone who could be a political asset in delivering particular electoral votes.

But as this campaign season has demonstrated repeatedly, Trump's mindset can change quickly, depending on the influences bearing down on him, the circumstances he confronts at any given moment and his personal rapport with an individual.

"You've got to be flexible," he's said often on the campaign trail, referring to business dealings or legislative wrangling.

There's no reason to believe that tenet won't be applicable to the vice presidential process – and while there will be plenty of advice dispensed, aides stress that the ultimate choice will be Trump's and Trump's alone.

Based on reporting from inside the campaign and discussions with outside influencers, here's an early VP scouting report of who's on Trump's mind for the No. 2 slot.

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Quick take: The Tennessee senator was one of the first establishment-aligned voices to step out and praise Trump after his scripted foreign policy speech last month in Washington. Having carefully never placed a foot in the anti-Trump camp, he's clearly open to lending the New York businessman his expertise on foreign policy, and unlike many others, hasn't ruled out accepting the slot.

Resume: Second-term U.S. senator, chairman of the Senate Foreign Relations Committee

Pros: In praising Trump for challenging Washington's foreign policy establishment, he appears more in line with the presumptive nominee's unconventional worldview than previously believed. He satisfies two chief requirements: knowledge of foreign affairs and policy experience in the nation's capital with designs on problem-solving. Additionally, he shares a construction background with Trump, which could provide cohesion.

Cons: Seen as a centrist and a dealmaker, he may irk members of the right-wing base. While he has two successful statewide election bids under his belt, his national political chops are unknown, so some insiders have said he may be a better fit as secretary of state.

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Quick Take: A Trump confidante says Flynn's name has come up in recent conversations with the candidate, who finds the retired Army lieutenant general "dynamic and impressive." An outspoken critic of President Barack Obama's foreign policy, Flynn has advised Trump informally on matters of national security and global affairs, particularly relations with Russia.

Resume: Former chief of the Defense Intelligence Agency

Pros: He checks the national security box for Trump, lending him immediate credibility within conservative circles and with military brass. He also has experience dealing with Capitol Hill.

Cons: Too much testosterone on one ticket. "I think Flynn and Trump are two peas in a pod," a former senior U.S. intelligence official who knows Flynn told The Daily Beast. "They have this naive notion that yelling at people will just solve problems."

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Quick Take: The former secretary of defense has also piqued Trump's interest, especially since he wouldn't completely rule out working with Trump in an interview with CBS News. "I learned a long time ago never to say never, but let's just say that would be inconceivable to me," he said.

Resume: Former secretary of defense under Presidents Obama and George W. Bush

Pros: Immediate cross-partisan credibility on national security and defense issues, and would serve as proof a skeptic could be won over.

Cons: He's previously praised Hillary Clinton and was aligned with her on several foreign policy quandaries during the Obama administration. And the transition from diplomat to candidate hasn't always worked out: The skills required to handle the fire of a 24-hour Twitterized media environment is a different set than those attuned to a battlefield.

(Alex Wong/Getty Images)

Quick Take: The former speaker of the House has acted as an informal liaison between Trump and Washington for months now, and his frequent appearances on Fox News betray a notion that he'd gladly serve if called upon. A Trump ally tells U.S. News that casino magnate Sheldon Adelson – an ardent backer of Gingrich's 2012 presidential run – recently brought up Newt's name in his private meeting with Trump.

Resume: Former U.S. speaker of the House

Pros: He's a smart and wily tactician, he can debate, and he brings heft on policy and an intricate knowledge of Congress. He's also run for president before, which matters when the lights burn bright. Fox News' Sean Hannity has become a nightly cheerleader for Gingrich, handing him a powerful advocate on the right.

Cons: Twice-divorced himself and saddled with allegations of affairs, he'd reinforce the anti-woman tag that Democrats are already gleefully slapping on Trump for his own personal peccadilloes. With the release of a new book, Gingrich may be leveraging the Veep speculation to gin up sales.

The Associated Press

Quick Take: Some familiar with Trump's thinking believe he's less likely to select one of his former rivals based on the body language they notice when he refers to them. One adviser worries New Jersey Gov. Chris Christie is a high risk for "embarrassment" due to the ongoing Bridgegate investigation. But of all of Trump's 16 competitors, Kasich may be the most likely to end up on the ticket.

Resume: Two-term governor of Ohio, former congressman

Pros: Ohio, Ohio, Ohio. He (likely) locks down the Buckeye State's 18 electoral votes, which are a must-win for any GOP candidate. Kasich also brings deep Capitol Hill ties from his stint in Congress and could help soften up Trump with his more inclusive, moderate tones.

Cons: His quote to CNN in February shooing away interest was quite the indictment of himself: "I'd be the worst vice president anybody could ever imagine. I'd be worse than Biden, because I'm my own man. I'm not going to take orders from these people. It's not what I do, it's not who I am."

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Quick Take: Trump has said at least one woman is on his list, but when he heaped praise on Brewer, it sent shivers down the spine of some allies, who recall how she froze on a debate stage during her 2010 re-election bid. Without a large number of female options – New Mexico Gov. Susana Martinez has indicated she'll be a hard sell – he may turn to Fallin, who is largely unknown on the national scene.

Resume: Oklahoma governor and two-term U.S. House member

Pros: She's a woman and could be a Hail Mary pass aimed at helping Trump shrink his gaping gender gap against Clinton. Trump's already lauded her as a "fabulous person" and she's already gotten a hang of the sloganeering, saying she'd be "honored ... to receive a call saying, 'I need you to help make America great again.'"

Cons: She's a woman, and Trump's selection of her may be too cute by half and seen as a token pick meant to pander to the fairer sex. She's also fairly untested nationally, packing almost a Palin-level like risk.