Donald Trump’s press conference with Vladimir Putin this week is likely to go down as one of the signature moments of his presidency. In an appalling display, the US president refused to endorse the verdict of his own intelligence agencies that Russia had deliberately intervened in the 2016 US presidential election. Instead, he gave equal credit to the “extremely strong and powerful” denial of such interference issued by President Putin. Mr Trump followed this up with a baffling and self-serving rant against his domestic critics — name-checking all his usual foes from Hillary Clinton to the FBI.

This kind of display from Mr Trump is an embarrassment when it happens at home. Coming at a summit meeting with the Russian president, on foreign soil, it ranks as a betrayal of the American national interest.

Mr Trump has undermined his country and his office in a series of important ways. His performance in Helsinki made it absolutely clear that the US president places his own political survival and personal vanity above any belief in the rule-of-law. Just a few days earlier, Rod Rosenstein, America’s deputy attorney-general, had indicted 12 Russian agents accused of interfering in the 2016 election and had correctly pointed out that the indictments should not be a partisan issue. But this crucial point is lost on Mr Trump. Everything — including truth, the rule-of-law and the dignity of the US — is subordinated to his own partisan interests.