In his home state, Mike Pence gazed out at the massed ranks of the National Rifle Association.

“I know we’re going to keep on winning because I have faith – faith in this president I serve alongside every day,” the vice-president said, his breathing audible on the microphone. “I mean, I got to tell you, somebody said to me the other day: ‘Tell the president to keep on going, keep on fighting.’ And I said to them: ‘That’s not something you got to tell him.’”

The stadium in Indianapolis erupted in laughter. Pence went on to praise Donald Trump’s “energy”, “leadership” and “fight” and refer to him as “my friend” in a 23-minute speech last month that mentioned “President Trump” 11 times.

It was a characteristic expression of devotion from the first of all the president’s men. To supporters, Pence, 59, is a loyal lieutenant smoothing Trump’s rough edges while steering America right. To critics he is a hypocrite and sycophant, the Uriah Heep of Washington. Columnist George Will wrote in the Washington Post last year: “The oleaginous Mike Pence, with his talent for toadyism and appetite for obsequiousness, could, Trump knew, become America’s most repulsive public figure.”

What’s his game? Why does a devout Christian agree to be Trump’s running mate and continue to be his apologist in chief? It might be pure craving for power. Pence has harboured ambitions of becoming president “since he was 16 and I’m sure it has not varied”, his biographer, Michael D’Antonio, said by phone this week.

“He is sure as sure can be that God put him in this place for that purpose. I have no doubt that he took the offer anticipating becoming president himself and I don’t think he’s a good enough student of history to know how difficult it has been for vice-presidents to become president.”

Though he is now a heartbeat away, D’Antonio said, Pence’s chances are slim. “Like Trump, he sees what he wants to see and it’s all about positioning. His record is so scant in Washington and what he did in Indiana is so bad that he would need divine intervention to win.”

That Washington record consists of six terms in Congress in which Pence was an early advocate of the Tea Party movement (“I was Tea Party before it was cool”) and a hardliner on issues such as abortion and LGBT rights. Elected governor of Indiana in 2012, he was criticised for a feeble response to an HIV outbreak and for signing “religious freedom” legislation that made it easier for conservatives to refuse service to gay couples.

Such actions helped make him a liberal bete noire, with some questioning whether a Pence presidency might actually inflict more damage on women’s and gay rights than the Trump one. He has also been mocked over reports that he refers to his wife Karen as “mother” and that he refuses to dine alone with other women.

Friends in Indiana, however, insist that he is misunderstood. Curt Smith, the president of the Indiana Family Institute, said: “He doesn’t hate anyone. If you went up to Mike Pence and said, ‘I’d like your advice on the best life possible,’ I think he’d say, ‘Follow the scriptures.’

“If you said, ‘Well, I have these same-sex urges and tendencies and leanings,’ he’d say, ‘Man, I’ve got a lot of problems in my life too and I’m fighting those. Welcome to the fight. But my advice is, do your darnedest to follow what God has given us in his holy word.’ There’s no hate in there; that’s loving your neighbour. If I believe that and I don’t tell you or someone else then I haven’t loved my neighbour.”

Charles Hiltunen, 57, who was at law school with Pence in Indianapolis, added: “I remember people used to make fun of him when a woman lobbyist would take him out and he would insist that there would be someone else or he would never go. Now you look at everything that’s going on with [the] #MeToo movement and I’m thinking: ‘He was brilliant.’

“He didn’t do that to protect himself. He probably did it also to protect the other person there. He’s way ahead of his time. Too bad we didn’t have more politicians with that set of standards, but there we go.”

‘Melting into the background’

Governor Pence was facing possible defeat in his bid for re-election when he was rescued by Trump’s invitation to join the 2016 ticket. He gave the smash-mouth New York celebrity businessman, a former Democrat who struggles to quote from the Bible, much needed credibility with conservatives and evangelicals.

Pence was at Trump’s side when he stunned the world by beating Hillary Clinton and he has been there ever since. The vice-president plays an outsized role in foreign policy – steering aid to Christians and other minorities in Iraq, for example – while artfully keeping his head down during one domestic crisis after another. Even the special counsel Robert Mueller left him relatively unscathed.

D’Antonio, the co-author of The Shadow President: The Truth About Mike Pence, said: “Pence has a longstanding practice of stepping aside when something bad is about to happen. He’s very good at melting into the background and not being present when the worst occurs so that he can have deniability. ‘How do I avoid full accountability and not have my failure noted?’”

Yet Pence has been careful to ensure that such body swerves are not construed by Trump as disloyalty. He is ostentatious in his displays of fealty, smiling beatifically at his boss, peppering his speeches with praise and even imitating his water drinking habits at meetings. Kenneth Adelman, a former Reagan official, told the Atlantic: “I’d like my wife to look at me just for one day the way Mike Pence looks at President Trump every day they’re together. That would be special.”

According to the Atlantic, the outward shows of devotion are mirrored in private, as Pence seldom disagrees with Trump in staff meetings. In one alleged episode, when the then chief economic adviser, Gary Cohn, spoke out against the president’s failure to condemn white supremacists in Charlottesville, Virginia, Pence remained silent, only to later visit Cohn’s office and tell him: “I’m proud of you.”

What remains unknown is whether Pence’s prayers contain similar confessions of conscience. In Indianapolis on Friday, he repeated his oft-used line: “I’m a Christian, a conservative and a Republican, in that order.” Yet he has tethered himself to a president whose behaviour often seems to trash the Ten Commandments. Pete Buttigieg, the mayor of South Bend, Indiana, and a Democratic candidate for president, wondered last month: “How could Pence allow himself to become the cheerleader of the porn star presidency?”

D’Antonio said: “I think he’s resigned to it. In his head, I’m sure he’s saying this is the deal I made. In archly conservative Christian circles there’s a lot of talk about how this is like a biblical imperative: that Trump may be an imperfect vessel but he’s carrying forward the mission of believers. So he himself is ugly and does ugly things in service to a greater cause.

“And this is the thing that [press secretary] Sarah Sanders, I am sure knows and does because her father is a pastor from this stream of Christianity, and it has to do with ‘the justified lie’. The Catholic church has a bit of theology about this too where it’s OK to sin in certain circumstances, so that there is almost a mass self-delusion that’s practised by people in Pence’s world around this issue. He sees it, I’m certain, as his job to defend what Trump is doing big picture by excusing every appalling thing that he does.”

This will weigh on Pence and his wife, Karen, as they consider whether he should mount a future run for president, D’Antonio added. “I think they consider all of this ugly and unseemly and there’s probably a great big concern on Pence’s part when it comes to eventually establishing a difference and some distance between himself and the president.

“He’s very well connected nationally so I think he believes that he could somehow activate his network and base and mount a credible campaign and I think he could. What’s interesting about it is that he would be Trump without the overt racism but I don’t know that you could win as that candidate. I find him really unnerving.”

‘He believes in divine intervention’

The former White House aide Omarosa Manigault Newman speculated that Pence is biding his time until Trump resigns or is impeached. To others who know him, he is rather a believer in manifest destiny. If it God’s will that he occupy the Oval Office some day, he will not resist.

Hiltunen, a principal at the lobbying firm Sextons Creek, said: “He believes truly that if it’s meant to be, it’s meant to be, but I don’t think it’s a personal ambition of his. If he’s led in that direction, he will. That’s where he believes in divine intervention – just think about what it takes to become president of the United States.

“His spirituality runs so deep in his belief system that I think he believes that everything happens for a reason. He is a true believer and I think he lets those principles guide him in everything he does.”

Pence’s favourite movie is reportedly The Wizard of Oz. Mike Murphy, a former Republican party chairman in Indiana, suggested that, beneath the granite, self-righteous exterior, there is a more playful human being.

“He’s a funny guy,” he said. “He does impressions and can sketch your caricature in a few minutes.

“He has a sense of humour and boyishness but that’s been driven out of him by message discipline. He’s probably the most disciplined politician I know and it takes away any sort of humanness and spontaneity.”

Murphy, who could not bring himself to vote for Trump or Clinton in 2016, acknowledged that Pence must wince whenever the president hurls vulgar insults at rallies or in tweets.

“I think he probably struggles with it every day and tries to mitigate the president’s treatment of people. The question is, which is dominant: his Christian faith or his ambition? Do those two parts of his brain seamlessly blend or is there a red line between them?”