WASHINGTON (AFP) - Mike Pence is the loyal wingman, the ever-discreet figure who rises above the Washington fray. But as the Russia scandal encroaches ever further on Donald Trump's White House, the vice-president is also walking a political tightrope.
The 58-year-old former governor of Indiana is currently the man closest to the US presidency - either as Trump's immediate successor should his term end prematurely, or as his heir apparent in 2020 or 2024 elections, depending on how many terms Trump serves.
As the troubles of his boss grow deeper by the day, ensnared in a widening investigation into his campaign ties to Russia, experts say the 48th US vice-president remains compelled to stand by his man - at least for now.
"Pence is in a very difficult position," Joel Goldstein, an expert on the vice presidency at Saint Louis University School of Law, told AFP.
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"A vice-president is expected to be loyal to the president, but President Trump imposes a heavy burden on his subordinates by saying and doing things that often are hard to defend."
The two men could hardly be more different: where Trump likes to blur ideological lines, Pence is a committed Christian conservative, as stiff and disciplined as his boss is exuberant and unpredictable.
While Trump tweets about a high-stakes healthcare bill, it is Pence who has been shuttling between the White House and Congress in a behind-the-scenes effort to rescue the imperiled legislation.
In Trump's turbulent Washington, Pence is seen as the administration's steadying force, the "ax behind the glass you're supposed to break in case of emergency", as The Daily Beast news website put it recently.
Pence offered a glimpse Wednesday (July 12) of what it's like on the Trump rollercoaster, as number two to arguably the most controversial US leader in modern times.
"You need to keep your arms and legs in the ride at all times," he told student leaders at American University.
"Pull the roll bar down, because you just got to hang on."
Yet Pence has taken low-key steps that suggest he could be laying the groundwork for his political future.
In an unusual move, two close advisors to Pence have founded a political action committee, The New York Times reported.
He has also begun hosting Republican mega-donors at his Washington residence, according to the daily.
As federal and congressional investigators dig deeper into allegations that Trump's camp colluded with Russia to tilt the 2016 election, a handful of Democrats are now calling openly for the president to be impeached.
However remote the prospect of impeachment by the Republican-controlled Congress, the Russia cloud stubbornly refuses to dissipate.
Should Trump eventually be forced from office, Pence would become the 10th US vice-president to assume the presidency without being elected - the first since Gerald Ford succeeded Richard Nixon following the Watergate scandal in 1974.
When Donald Trump Jr recently acknowledged that he and campaign aides met a Russian lawyer last year in hope of obtaining dirt on Trump's Democratic rival Hillary Clinton, Pence distanced himself from the snowballing scandal.
"He is not focused on stories about the campaign, particularly stories about the time before he joined the ticket," said a statement from Pence's office.
But the vice-president has not emerged entirely unscathed so far.
As head of Trump's transition team, he publicly backed Michael Flynn during the uproar about contacts with the Russian ambassador which cost the newly-minted national security advisor his job.
And having flatly denied any Trump campaign contacts with Russia, Pence's credibility is further rocked with each new revelation.
Pence's defense will look increasingly questionable, especially if Trump's troubles worsen. But it is survivable, said Michael Munger, director of the politics program at Duke University.
"Pence was probably not lying. He was lied to, and he took the party line and then kept his mouth shut when they cut him off at the knees," the professor said.
"He is losing credibility, I suppose, but he gets extra points for doing his job." Yet Pence's close ties to the president - as recently as last month he said serving with Trump has been "the greatest privilege of my life" - may yet prove an albatross around his neck.
"None of the last seven vice presidents have been so willing to be so sycophantic in their praise and have said so many significant things that later turned out to be untrue," the expert Goldstein said.
Striking the balance between loyalty to an embattled leader and avoiding getting caught up in scandal is a fierce challenge.
Pence has "juggled" well, said Paul Beck of Ohio State University.
"But if this Russia controversy really gets the Trump administration into deep, deep trouble... then Pence is kind of trapped out there as one of the team."