“Is it just two ships passing in the night?” Mr. Sabato asked about the sudden enthusiasm about the economy.

Maybe. Historically, Americans have swung behind any newly elected president, with partisan divisions and more realistic expectations resuming after a honeymoon period. In 2008, after President Obama’s election, for example, optimism about the economy was even stronger despite the financial collapse of the time.

But Wall Street and business are particularly pumped by the prospect of an end to Washington gridlock. Stephen A. Schwarzman, the chief executive of the private equity giant Blackstone and chairman of Mr. Trump’s panel of business experts, said at an investor conference that change was coming.

“I anticipate with a pretty high level of confidence that this stuff is going to happen,” he said. “And this is as big a change happening all at once — I’ve been in finance for, I don’t know, 45 years? This would be the biggest.”