Joe Biden delivered. There was no somnolence, no quiescence. Instead, Biden lashed into his predecessor in unprecedented fashion to offer the most important speech of his presidency.

It was a well-struck blow. Donald Trump cannot take Biden’s speech detailing his serial infamies lying down. Biden’s remarks were calculated to nettle, inflame and enrage Trump into further tipping his hand, such as it is. Biden, who was careful never to dignify him by mentioning his actual name, depicted Trump as a dissembler, a knave, a poltroon, a “remorseless, treacherous, lecherous, kindless villain” of Shakespearian proportions who is...

Joe Biden delivered. There was no somnolence, no quiescence. Instead, Biden lashed into his predecessor in unprecedented fashion to offer the most important speech of his presidency.

It was a well-struck blow. Donald Trump cannot take Biden’s speech detailing his serial infamies lying down. Biden’s remarks were calculated to nettle, inflame and enrage Trump into further tipping his hand, such as it is. Biden, who was careful never to dignify him by mentioning his actual name, depicted Trump as a dissembler, a knave, a poltroon, a “remorseless, treacherous, lecherous, kindless villain” of Shakespearian proportions who is scheming, as far as possible, to subvert American democracy, whenever and wherever he can.

Trump, it must be said, offers precisely what most American presidents crave but usually don’t receive — a cartoonish enemy that they can rally the nation against. Trump, you could say, is a deliverance for Biden. He allows Biden to transcend his essentially humdrum nature, his Babbitry to stand as the avatar of decency and truth. Give Trump credit. His transparent nefariousness allowed Biden to win one election. It might well allow Biden to win another in 2024. The speech that Biden delivered at the Capitol was his unofficial announcement that he’s running again.

Biden’s fundamental insight was to flip the script. Republicans have often depicted Democrats as cowardly ninnies, unpatriotic and anti-American. Now Biden depicted the former guy as a repository of those sentiments. He would let no one, Biden declared, aim a “dagger at the throat of American democracy.” The notion that only one side can win an election was nonsense: “You can’t love your country only when you win. You can’t obey the law only when it is convenient. You can’t be patriotic when you embrace and enable lies.”

True to form, Trump was having one of it. Banned from Twitter, he can only issue snarling press releases, which he did. “Everything he touches turn to failure,” Trump wrote. “That’s what you get when you have a rigged Election.”

But Trump, a brand salesman par excellence, knows that Biden has found his voice. Biden has the bully pulpit. He’s going to be bullying Trump.

The two men need each other. The higher profile Trump remains, the more rallies he holds, the better Biden will look in comparison. Now more than ever, Biden needs Trump to validate his presidency. For the past year, Biden sought to ignore Trump. His poll numbers plummeted. His speech showed that he is bowing to reality. Like Sherlock Holmes grappling with Professor Moriarty, Biden cannot extricate himself from Trump. Trump looms larger than ever.

But there is a huge upside for Biden. As he wanders among his baubles at Mar-a-Lago muttering about a stolen election, it may eventually dawn upon Trump that he has become Biden’s unwitting confederate. If Trump didn’t exist, Biden would have to invent him.