Economists, too, find their outlook shifting with the political landscape. Before the election, Heather Boushey, a top adviser to Hillary Clinton during the campaign, thought “the economy was on the right track, with slow and steady growth like we’ve had over the past few years.”

Now she is much more pessimistic, especially about the economy’s long-term prospects. Although she is pleased that the Affordable Care Act survived Republican efforts to repeal it, the gridlock has led her to believe that Mr. Trump will never get a big infrastructure spending package through Congress.

“I am losing hope that we will make those much-needed investments over the next few years,” said Ms. Boushey, executive director of the liberal Center for Equitable Growth.

The University of Michigan researchers have their own way of measuring the gulf between the two viewpoints and how quickly it has flipped.

Among Republicans, the Michigan consumer expectations index was at 61.1 in October, the kind of reading typically reported in the depths of a recession. Confident that Mrs. Clinton would win, Democrats registered a 95.4 reading, close to the highs reached when her husband was in office in the late 1990s and the economy was soaring.

By March, the positions were reversed, with an even more extreme split. Republicans’ expectations had soared to 122.5, equivalent to levels registered in boom times. As for Democrats, they were even more pessimistic than Republicans had been in October.

As at the voting booth, the split in perceptions could have real-world consequences. If behavior tracks the recession-era sentiment among Democrats, who account for 32 percent of respondents in the survey, prophecies could quickly become self-fulfilling by affecting spending and investing decisions.