US Senator John McCain’s verdict on US President Donald Trump’s performance at the summit in Helsinki was brutal, but just: “No prior president has ever abased himself more abjectly before a tyrant.”

Standing alongside Russian President Vladimir Putin yesterday, Trump failed to support his own government’s unequivocal assessment that Russian military and intelligence agents mounted a cyberattack against the US throughout the election of 2016 — an elaborate effort to sabotage America’s democracy.

Only a few days earlier, a grand jury convened by special prosecutor Robert Mueller had indicted a dozen Russian agents for the attack. The indictment identifies criminal details down to individual keystrokes on Russian computers.

US Director of National Intelligence Dan Coats, a former Republican senator, said on Friday: “The warning lights are blinking red again. Today, the digital infrastructure that serves this country is literally under attack.”

Asked about those attacks, Trump said: “My people came to me, Dan Coats came to me and some others, they said they think it’s Russia. I have President Putin, he just said it’s not Russia. I will say this: I don’t see any reason why it would be.”

The implication is that Putin is a more credible source of information about Russian skulduggery than the combined intelligence agencies of the US Government.

Trump also spoke warmly of Putin’s “incredible offer” to have Russian investigators help out with the case. Incredible is the word.

Asked why relations with Russia are bad, the US President, in a tweet, blamed “US foolishness” — as opposed to the assault on America, Russia’s invasions of Ukraine and Georgia, the killing of innocents in Syria, and efforts to undermine democracy in Europe.

In all, it was an astonishing display, and one that should leave the President’s supporters in Congress and the nation alarmed.

A country can hardly defend itself against future assaults if its President can’t acknowledge the ones that have already taken place.