Washington (CNN) Vice President Mike Pence's last-minute September meeting with the Ukrainian President has pulled him into a mess he has worked hard to avoid: a crisis involving his boss, President Donald Trump .

Rather than traveling to Warsaw, Poland, last month to meet with Ukrainian President Volodymyr Zelensky, Trump decided to stay home to track the damage from Hurricane Dorian. In his place he sent Pence, whose face-to-face meeting with Zelensky now puts him at the heart of events that led to the impeachment inquiry by the House of Representatives.

Trump isn't making it easy for Pence to distance himself, even suggesting that the details of Pence's phone calls and conversations with Zelensky should be released.

"I think you should ask for Vice President Pence's conversation, because he had a couple conversations also," Trump told reporters last week after the release of the White House transcript of his own July 25 call with Zelensky.

On Wednesday, The Washington Post reported that Trump has involved Pence on multiple fronts in his interaction with Ukraine.

Pence did not mention to Zelensky the President's unfounded allegations against Joe Biden in regard to Ukraine, according to a person familiar with the situation. "There was no reason to bring up Biden," the person says.

Pence aides maintain that when he went to Warsaw he was unaware of the Biden allegations being made by the President's lawyer, Rudy Giuliani. But one of the vice president's top aides had listened in on the call the President had with Ukraine's leader, according to a source familiar with the matter, confirming a report in The Washington Post.

Instead, according to one of the sources, the vice president spoke broadly about corruption in Ukraine and received assurances from Zelensky that he would crack down on it. Pence took that message back to Trump and helped convince him to release the aid to Ukraine, according to three senior administration officials. That, along with pressure from Congress, was a key factor in Trump's decision to finally support the release of $391 million to Ukraine after a months-long delay on the money, these sources say.

"The President consistently raised concerns about corruption and the lack of burden sharing by European partners, so having run on an anti-corruption campaign, Zelensky was receptive to those messages," said Marc Short, Pence's chief of staff. "The vice president reported back to the President after the meeting and the aid was released."

"We do not comment on conversations between the President and the vice president," Short said.

Pence frustrated

Recent conversations with a person close to the matter reveal a deep level of anxiety inside the vice president's office. Pence advisers are frustrated with how the White House has handled the fallout from the Ukraine disclosures, including bringing the vice president into the mess. An additional Pence adviser tells CNN, "It's a challenging environment," in response to the controversies and scandals the vice president has had to dodge, most recently Ukraine.

There is also concern within Pence's team over his standing with Trump.

Publicly Trump has consistently praised the vice president, insisting Pence will be his running mate next year, yet privately he is more circumspect. One person close to Trump says he is cagey when it comes to whether he will keep Pence on the ticket, always cautious not to tip his hand one way or another.

One Pence adviser pushed back on that, telling CNN that privately Trump has asked Pence to stay on the ticket.

Regardless, the challenge for Pence, as it's always been, is balancing the need to appear loyal to Trump with staying clear of the President's countless controversies. The plan to protect him, according to sources close to the vice president, is to get him on the road. On Wednesday Pence traveled to Arizona, where he attended events in Tucson and Scottsdale alongside Republican Sen. Martha McSally.

This strategy is largely in keeping with the traveling envoy role Pence has inhabited for much of the past year. During the spring and summer, he was busy flying around the country to talk up the administration's North American trade deal, the USMCA. From March through August, Pence attended 26 separate events, from CEO roundtables to Midwestern factories.

Interviews over the past several months with more than 15 sources shed light on what was always a forced union between Pence and the President.

Pence remains a crucial link for Trump to evangelicals, a segment of the Republican base he will need in 2020. Yet temperamentally, the careful and scrupulous vice president couldn't be more different from a commander in chief who prefers to make decisions on the fly.

"Whenever the vice president does anything with foreign leaders, he is totally buttoned up -- prepared note cards, legal (advisers) present," a source familiar with the matter said. "He has always been squeaky clean," the source added, drawing a contrast with Trump's more freewheeling style on the calls.

Beyond their political relationship, Trump and Pence have little in common. Pence, hardly a scratch golfer, has only recently taken up the game Trump loves. While Trump frequently starts his day turning on cable news and firing up his Twitter feed, Pence begins each morning reading his Bible.

In his 2019 book "Let Me Finish," former New Jersey Gov. Chris Christie describes brokering the first meeting between the men at the governor's mansion in Indianapolis shortly before the Indiana primary in March 2016. At the end of their meeting, Pence surprised Trump by asking the small group to join hands and pray.

"Does he do that all the time?" Trump asked Christie afterward. When Christie told him yes, the New Jersey Republican says, Trump responded with one word: "Interesting."

A devoted deputy

As the midterm election returns came in on the night of November 6, 2018, Trump began asking people, "Do you think Pence is good for me?"

While Trump didn't overtly criticize Pence that night, it was clear that the President was wondering what Pence contributes to his coalition. A close ally of Trump's stressed to him that Pence's steady presence and even keel made him the perfect running mate and vice president. The ally likened Pence to "a sommelier who doesn't drink."

Trump seems to have listened, jokingly asking in his post-election news conference the next day if Pence would be his running mate in 2020. Pence stood up and wordlessly agreed to do so.

"Thank you, OK, good," Trump said.

For a President who values personal loyalty above all, Pence has been nothing if not publicly and privately devoted to Trump. He has not spoken out to counter or undercut Trump -- not following the President's comments after Charlottesville, not during Trump's attacks on members of his Cabinet and not when Trump criticized Paul Ryan, one of Pence's closest friends from his time in Congress.

One source who once worked in the White House with the vice president says the guiding principle for Pence is unwavering fealty, in recognition that he would not be in power without Trump. Pence's model is George H.W. Bush, who loyally served alongside Ronald Reagan without any daylight between the two former rivals. The source says that if Pence has disagreements with Trump, he shares them privately.

Short, Pence's chief of staff, told CNN late last year that the vice president has avoided pushing forward his own pet projects or issues. "He would never say, 'Here's my agenda and here's how it fits in.' He's going to support the Trump agenda," said Short.

Moreover, Pence has taken on tasks that might be less interesting to Trump, such as international trips and leading the charge to create the Space Force division at the Pentagon. The idea, from the vice president's perspective, is to do whatever he can to endear himself to Trump.

A key to evangelicals

Most endearing -- or at least the most valuable -- to the President may be Pence's direct link to the GOP's social conservative wing. As a House member, Pence was active in a congressional Bible study and cultivated relationships with the politically active evangelical network in the nation's capital. People in that network say Pence is a key

"I found Mike Pence to be one of the like-minded and one of the most reliable people that I could work with in the Congress," said Dr. Richard Land, the president of the Southern Evangelical Seminary who was the longtime head of the public policy office of the Southern Baptist Convention. "He cared about the things that I as a Southern Baptist and the majority of Southern Baptists cared about."

Pence's record and reputation have continually prompted questions of how a devout Christian could continue supporting a President accused of having multiple extramarital affairs. Trump has denied having affairs with his accusers. Even those who have worked closely with Pence for years say he and Karen Pence are buttoned up on their true feelings about Trump's moral failings.

One clue comes from Jane Mayer of the New Yorker, who reported in October 2017 that Pence sent a letter to Trump just after the release of the "Access Hollywood" tape a month before Election Day 2016. Pence told the Republican nominee that he and his wife were offended by Trump's comments on the tape and wanted to reassess Pence's placement on the ticket.

However serious Pence was at that moment, those concerns appeared to have been allayed shortly thereafter. Publicly, Pence went on to say he was "grateful that [Trump] expressed remorse" for the comments on the video, and he remained on the ticket.

Pence's future in the air

If the President keeps Pence on the ticket through 2020, as expected, it will be for the political utility he provides Trump. He's already resumed the role of top Trump campaign surrogate as the 2020 reelection effort ramps up, working to woo the traditional groups like donors and trade groups to the Keep America Great cause.

What remains Pence's competitive advantage is his long-standing connections with the broader conservative movement, which remains an integral part of the Republican coalition. Pence is a particularly important bridge to the politically active evangelical community, that network of activists and donors that has prioritized issues like abortion, religious freedom and judicial nominations.

"I would say that it's a wonderful thing to have someone of Mike Pence's caliber and integrity as vice president of the United States," said Tim Goeglein, a White House official under George W. Bush and a vice president at Focus on the Family. "It's a very good and very helpful thing that we can express our views to someone who shares our views on things like human life and on issues of judges and the Supreme Court and other issues of that nature."

Goeglein, who has known Pence for 25 years, said the vice president has been one of the most important champions for evangelicals in Washington in years. "He's someone we know and someone who we trust," Goeglein said.

A member of the Trump campaign's evangelical advisory board in 2016, Richard Land recalled being asked that summer what his first piece of advice for the Republican candidate would be. Without hesitation, Land answered, "Pick Mike Pence."

"It was the first thing that popped into my mind, because I could think of nothing which could more assure evangelicals that they were going to have a seat at the table in the Trump administration than making Mike Pence his vice president," Land told CNN.

Neither Goeglein nor Land put much stock in the idea that Trump might replace Pence, though the latter says he fears doing so could hurt the President among evangelical voters. "That would be a problem," said Land. "I think it might depress [turnout] some."

That might be enough reason for Trump to keep Pence around, but Pence offers one more critical benefit to the President: his willingness to completely submit himself to Trump and his agenda.

"He's very loyal to the President," said Pence's close friend, former Republican Rep. Jeb Hensarling of Texas. "He's always had a kind of orientation to authority."

This story has been updated.