It is extraordinary, in retrospect, that Mike Pence wouldn’t have known about Michael Flynn’s conversations with Sergey Kislyak or his foreign lobbying ties. As we now know, multiple members of the Trump campaign were aware that the man who would become Donald Trump’s national security adviser was in communication with the Russian ambassador at a senior campaign official’s behest. Yet Pence, who was in charge of Trump’s White House transition team—directing staffing, organizing agency “landing teams,” and vetting administration candidates—was conveniently out of the loop. (Flynn was ostensibly fired for misleading the vice president about those contacts.) Pence went radio silent again last week, when Flynn pleaded guilty to lying to the F.B.I. about those conversations. And he was nowhere to be found in the aftermath, as Trump’s legal team raced to contain the fallout after the president potentially implicated himself in obstruction of justice on Twitter.

Pence’s recent absenteeism is only the latest evidence of a delicate balancing act the vice president has maintained since joining the ticket last year. The former Indiana governor has, on the one hand, secured Trump’s trust by serving as an unflappable, unquestionably ideological defender of the president’s agenda. But his blissful ignorance on all things Russia has also raised eyebrows in Washington among insiders who see him as the obvious back-up candidate if Trump doesn’t pan out. Indeed, Pence has a curious pattern of alibis whenever controversy strikes the West Wing. While Flynn and Jared Kushner were ensnared in back-channel brokering over a United Nations resolution during the transition, Politico notes, Pence was volunteering at a homeless shelter in his home state of Indiana. When Flynn was gabbing with Kislyak about lifting sanctions against Moscow, Pence was at his son’s wedding. As Donald Trump Jr. was fending off headlines about his Trump Tower meeting with Natalia Veselnitskaya, his father’s right-hand man insisted that was the first he’d heard of it.

Rumors of Pence’s presidential ambitions seem to resurface whenever Trump’s political prospects look weakest. As I reported earlier this year, in the wake of Robert Mueller’s appointment, Pence would make for a natural Republican successor in the event of impeachment, and not just because the constitution would give him an inside track. “He is an ideologic rock, and I think he has continued to be that in every way,” Rex Elsass, a top G.O.P. strategist and ad maker who worked with Pence in Indiana told me. “He’s done his job and been loyal to the president and is able to be someone who is seen as the ideologic heart of the administration.” Others noted the existence of an unspoken agreement among Republicans to keep Pence above the fray. “He’s not stupid about the fact that there could be some very bad outcomes for Donald Trump here,” Rick Wilson, another Republican strategist, added. “The guy is capable of putting together a kind of long-term game plan.”

There is no vice president who takes the job without the expectation of advancement. But Pence, it seems, glimpsed the possibility of a promotion early on. According to The Atlantic, amid the tumult after the Access Hollywood tape was made public, Pence briefly came within spitting distance of the top of the Republican ticket. Several Republican sources familiar with discussions at the time told the outlet that the then-vice presidential nominee signaled to the Republican National Committee that he was open to replacing Trump as the G.O.P. nominee, with Condoleeza Rice as his running mate. (An aide to the vice president denied that Pence ever discussed becoming the nominee with the R.N.C., and Reince Priebus, who also reportedly floated the plan, did not respond to the magazine’s requests for comment.)

It is a grand irony that Donald Trump might, unintentionally, slingshot Mike Pence to the presidency. While Pence’s name emerged as a potential presidential contender for 2016 in the wake of his 2012 gubernatorial victory, the Indiana governor’s political career was on a downward trajectory when he unexpectedly hitched his wagon to Trump’s star. Pence bled support on both the right and the left after his notorious flip-flop on the controversial Religious Freedom Restoration Act; he was struggling with an H.I.V. epidemic and a prolonged lead-poisoning crisis; and he was facing a brutal re-election bid after signing an unconstitutional anti-abortion bill into law. Trump provided Pence an out; Pence provided Trump a glimmer of establishment respectability. Among Republicans on Capitol Hill, major party donors, and social conservatives, his credibility was unimpeachable.