If anyone still held out hope that the awesome responsibilities and dignity of the presidency might temper or even humble Donald Trump, there was a shock from his first news conference as president-elect, on Wednesday. Bombastic, vain and slippery, Mr. Trump played the same small-screen character he has offered the viewing public for years.

Presenting himself as the leader of “a movement like the world has never seen before,” he offered no olive branch to the majority of American voters who opposed him. He displayed only petulance and braggadocio in response to issues that dogged him during the campaign.

On suggestions that he had business dealings with Russia: “I tweeted out that I have no dealings with Russia.” He ducked and dodged when reporters asked whether he or members of his staff colluded with Russia before the election — one of the most explosive of the charges swirling around him.

On his promise to reveal his tax returns, which could prove he has no financial or business ties to Russia: “I’m not releasing the tax returns because as you know, they’re under audit.” He added, “You know, the only one that cares about my tax returns are the reporters, O.K.?”