This 12 months Mr. Trump once more carried the district. In 2022, Mr. Cartwright mentioned, a Trump-style Republican in Pennsylvania’s elections for governor and Senate may win statewide. “A lot of it will depend on how life goes in two years,” he mentioned.

One other area that mirrored the shifts of latest elections, Saratoga County in upstate New York, was dwelling to one among Mr. Biden’s most decisive performances in a pivot county. Mr. Trump gained there by 3.2 factors 4 years in the past. Mr. Biden gained by 5.4 factors final month, for a complete swing of 8.6 factors.

Todd Kerner, the chair of the county Democrats, attributed the about-face to misgivings concerning the president by college-educated voters within the prosperous suburbs of Albany, within the southern finish of the county.

Jim Esterly, a retiree in Clifton Park, N.Y., was one among them. 4 years in the past, he mentioned, he was taken by Mr. Trump’s TV persona from “The Apprentice.”

“I mentioned, ‘Right here’s a man who’s a businessman,’” Mr. Esterly mentioned. “He’s had companies that failed, however he’s come again. I don’t know the way he righted the ship, however I mentioned working the nation is like working a giant enterprise.”

Disillusion set in early for Mr. Esterly, 68, who had managed a municipal wastewater therapy plant. “He didn’t imagine in local weather change,” he mentioned, citing the president’s withdrawal from the Paris accord. “When Covid hit, he was greater than silly, not believing his specialists early sufficient, then saying, ‘Perhaps we have to do one thing,’ then ignoring it.”

Mr. Esterly voted for Mr. Biden this 12 months, and he had loads of firm in suburban Clifton Park. Mr. Biden gained almost 3,000 extra votes within the city than Mrs. Clinton did in 2016. Mr. Trump elevated his help there by solely about 500 extra votes.