For this viewer, the meaning of the Trump show began to change with last week’s tax bill. Donald Trump normalizes nothing new and outré in our politics after all. He is but an effective parody of the politicians we have, and have long had.

We are also learning something about the relationship, in our age, between the political show and movement, however fitful, on the nation’s business.

Republicans’ performance at last week’s White House in celebration of the party-line tax bill may have been bombastic and obsequious, but the party placed its bet on a growing economy. The show, however odd, exploited the party’s star attraction, Mr. Trump, whom the cable channels can’t resist, to push out the message to America “good things are happening.”

Every bit as hysterical, excessive and embarrassing was the countershow put on by Democrats. But they put themselves on the side of bad things happening. Nancy Pelosi, Chuck Schumer and their junior shadows danced around the maypole, lighted candles, burned effigies—in hope that you will lose your job in 2018, see your hours cut, fail to get an expected raise.

This probably is an ill-advised bet by Democrats. The world’s major economies are in a synchronized upswing. The world’s central banks are using the window to withdraw their histrionic and destabilizing monetary accommodations of the past decade. To the extent that “it’s the economy, stupid” still trumps, the GOP will benefit.