As Donald Trump widened his pool of potential running mates this weekend, two candidates -- Mike Pence and Newt Gingrich - have seen their stock rise inside Trump Tower with less than two weeks until the Republican National Convention in Cleveland.
"Pence and Gingrich are the two that most fulfill Trump's acknowledgement that he wants to find a governing partner, someone who can pass legislation," an individual familiar with conversations about the vice presidential search told NBC News.
While discussion has intensified over the merits of the two potential picks, there is still vigorous debate within the campaign over other contenders in the mix, including Sen. Joni Ernst of Iowa, Sen. Bob Corker of Tennessee and New Jersey Gov. Chris Christie. And sources close to Trump caution that the decision ultimately lies with a candidate often known to place more emphasis on his own instincts than on the advice of others.
But inside the campaign, there's a vocal camp advocating for Pence, the governor of Indiana, who some believe could solidify Trump's support across the Midwest.
Sources also tell NBC News that Gingrich, who is actively being vetted for the role, has built a close working relationship with many in Trump's inner circle -- particularly Ivanka Trump and Jared Kushner, Ivanka's husband and now-key confidante to the presumptive nominee, speaking with both frequently and sometimes multiple times a day.
Gingrich, who maintained this weekend that he had yet to speak with Trump about the VP slot, has straddled a role as a trusted adviser to Trump while also publicly critiquing some aspects of his candidacy. And despite his close communication with Trump's family members -- and campaign chair Paul Manafort himself - some within the campaign remain cool to him as a potential pick because of what's seen as his uncontrollability as a campaign surrogate.
One source within the Trump campaign suggested that Manafort may not be enthusiastic about a Gingrich pick because he "cannot control a Gingrich, whereas he can control a Pence."
"I think that's a fairly obvious point — everybody knows what Newt's shortcoming could be on the ticket," said the individual familiar with VP conversations. "The theory is there are people who could fill that role without a lot of the liabilities."
And Gingrich himself is openly questioning his own desire to fill the role.
Asked by NBC News this weekend if he would "like" the VP job, Gingrich responded bluntly: "Listen, we'd be willing to consider it. Like is a pretty strong term."
Gingrich added that it remains Trumps job to "quit screwing up" and said that -- to take the VP job -- he needs assurances that he'd be aiding a president who is "deadly serious in a disciplined way about doing this."
Sources involved in the process confirm Gingrich remains privately uncertain that he wants to take the job.
But as Gingrich continues to, at times publicly, weigh the pros and cons of assuming a place on Trump's ticket, there are some internal forces that seek to push him out of the top tier as well.
One source within the campaign, who requested anonymity to speak freely on the issue, explained to NBC that when Gingrich's name started bubbling up as a possible heir apparent, new names - such as Pence's - were introduced to the conversation. "People in Gingrich World are scratching their heads," the source said.
Along with Pence, Trump met with Ernst over the weekend, and Trump tweeted praise for Sen. Tom Cotton's appearance on Meet the Press. And on Tuesday, Corker rallied with Trump at a campaign stop in North Carolina.
But a source with knowledge of the campaign's VP deliberations tells NBC that backers of Mike Pence have worked to sell him as the candidate who can shore up the Rust Belt in the general election.
"The idea of selecting Pence is to target pickups in the electoral college — nominate someone who gets you geography, get his or her state in your back pocket and decreases the number of swing states because they're strong in the region," the person said.
Pence's prospects for being selected have risen because of what he could bring to the ticket.
His home state of Indiana was just one of two states to vote for Romney in 2012 after voting for Obama in 2008, but Kellyanne Conway, a senior advisor to Manafort and part of the campaign's polling team, contended that Pence would give Trump the chance to take key states like Ohio, Michigan, Wisconsin, Iowa and Pennsylvania. Coal mining remains a major part of southern Indiana's economy.
"When Hillary Clinton promised to put the coal industry out of work in West Virginia, her shocking comment reverberated westward, across at least six or seven states, all which Pence could help in picking up one, two, three points right through the Midwestern states, where Romney bombed spectacularly," Conway said.
Those inside the Trump campaign are also looking at Pence because of his resume. Before running for governor in 2012, Pence had served 12 years in the U.S. House. For part of that time, he was the head of the House Republican Conference — number four in the party's House leadership, and he also worked for ten of those years on the House Foreign Affairs Committee.
Pence, a man with a calm but warm demeanor, is also not new to the media circuit -- he had, for years, his own syndicated radio talk show and a Sunday TV program in the Hoosier state.
There also may be reason for Pence to take the chance at the national level. He is up for his own gubernatorial re-election this November, squaring off in a rematch against the Democrat he faced four years ago and beat by just three percentage points.