The meeting between President-elect Donald Trump and Mitt Romney on Saturday was a seismic event.
The very fact that the two came face to face at all, let alone in a seemingly warm atmosphere, is a dramatic breakthrough, given the vicious way they denounced each other during the election campaign.
Mr Romney’s attacks on Mr Trump, an unprecedented onslaught from a former Republican Party presidential candidate (2012) against an impending one, were a calculated bid to stop the tycoon from succeeding just before he sealed the nomination.
The attempted political assassination was probably made only because of a feeling of confidence that Mr Trump would not reach the White House, and that such devastating public criticism (that Mr Trump was “a conman” without the “temperament” to be president, etc) would bury any faint prospect of success the New York billionaire had.
Other Republican leaders will have quietly cheered the verbal assault on Mr Trump, and some of them might even have acquiesced in it.
Mr Trump returned the venom with interest, as he does when he is criticised.
Disastrously for Mr Romney, his assassination bid failed, leaving his political future at the mercy of Mr Trump.
Soon we will see if an offer is forthcoming to make Mr Romney US Secretary of State, which is America’s foreign minister, or whether the meeting was merely a display of unity. Mr Trump is said to harbour grudges, and his electioneering tone gave that impression.
If he is prepared to overlook the vitriol of the campaign, and Mr Romney, 69, is offered and accepts the key diplomat post, the world will be a safer place than it otherwise might be.
During the long election campaign, Mr Trump said extraordinary things for a main party candidate, from praising the Russian leader Vladimir Putin to questioning the value of Nato.
Syria and Russia’s current heavy bombing of Aleppo might have been ordered in the context of the Trump win.
Four years ago I thought Mr Romney a smooth but almost shallow candidate for president. I wondered how an establishment political party in a superpower of over 300 million people, millions of whom are highly educated, had been unable to produce a more inspiring candidate for the leader of the free world.
But in the current context he is a figure of towering integrity and wisdom.
On Friday I wrote that some of the mooted Trump appointments gave hope that he might be pragmatic. I was thinking of people such as Mr Romney and the South Carolina governor, Nikki Haley.
But hours later Mr Trump unveiled hardline nominees for key posts, including General Mike Flynn as National Security Advisor, a man prone to incendiary rhetoric.
Mr Romney might fear that he cannot serve with credibility under a man he damned so witheringly. But it is to be hoped that he over-rides any such unease.
If he becomes America’s foreign affairs voice, he will be a calming figure in the Trump team’s most treacherous dealings: global relations.
• Ben Lowry (@BenLowry2) is News Letter deputy editor