ANALYSIS: If the last eight years have been any indication, acting vice-presidential consists largely of breaching people's personal space , throwing footballs and excessively using the word "malarkey" .

So when Mike Pence dons a bomber jacket and speaks to major countries about trade and national defence, it doesn't seem like the actions of a vice president.

More like the actions of a man posturing to take on the top job.

Liberals have been talking about impeaching Donald Trump since before he was actually sworn in, but in the face of a looming crisis with North Korea, conservatives are getting increasingly nervous.

Mike Pence speaks to Japanese and US servicemen aboard the USS Ronald Reagan in Japan. (AAP)

Business tax cuts and immigration bans may not antagonise the Republican-controlled Congress, but starting a war with North Korea certainly would.

Now Republicans are forced to confront the awkward prospect that Trump may be too erratic to serve as commander-in-chief .

And as the White House stumbles from debacle to debacle, Mike Pence is looking increasingly like a safe hand at the wheel.

Pence's biggest shortcomings - his charisma deficit, his instinctive caution and his predictability – are starting to look like serious strengths.

He may look like a small-town police chief being nice for his daughter's wedding, but that may just be what America is looking for after Trump.

Liberals may even forget Pence's deeply held conservatism if Trump is seen as putting the United States at risk.

While Barack Obama and Joe Biden became known as close allies and best friends, Pence is taking on a very different tack with the White House.

Pence is keeping the White House at arm's length, managing to steer well clear of any and every gaffe made by Trump.

Pence couldn't be further away from Trump right now without a spaceship. By visiting Australia , Japan and Indonesia, Pence looks like a diplomat and a warrior while Trump tees off at Mar-a-Lago .

Not that that's unusual for vice presidents to keep their distance. It's not unusual for running mates to totally despise each other. Obama and Biden were actually the exception to the rule in that regard.

Bill Clinton and Al Gore had a famously frosty relationship, and John F Kennedy and Lyndon Johnson were notoriously terse.

Worse still was Dwight Eisenhower, who balked at the prospect of Richard Nixon becoming his successor in 1960.

And with a president as unpopular as Trump is, Pence would be wise to keep his distance in case he needs to step up to the top job.

Mike Pence speaks at an event in Japan. (AAP)

Pence wants to learn the lessons of Gerald Ford, who moved into the White House after the resignation of Nixon.

Try as he did, Ford could not rid himself of the stink of Watergate and the Nixon administration. He would lose his first chance at a presidential election to Jimmy Carter in 1976 after pardoning Nixon for his various crimes.

So if the same thing happens to Trump, he can't hope for any such favours from his vice president.

Pence may well be practising saying: "Trump? Barely know the guy".