… Like Andrew Jackson in the first third of the 19th century, Mr. Trump is an unusual political figure, with no apparent successor of even remotely equal voltage. But the emergence of Trump as the GOP nominee has itself presented the Republican Party with either the threat or the opportunity to change its composition and its image, as the early Democrats did under Jackson.

“Parties continually change,’’ said former Republican governor Tom Corbett of Pennsylvania. “There are people in both parties who want something different. But I’m not sure they know what they want.’’

The Manhattan businessman appeals to a group of voters the Republicans have had difficulty attracting — working-class whites and those in sales and clerical positions. Along with the middle-finger voters, Americans with this profile have from time to time backed Republicans; they supported Reagan, for example, in 1980 and 1984. But they haven’t become enduringly aligned with the party. It’s possible Trump could move them into the GOP permanently.

“If that happened, and if it persisted, the Republicans would be a very different party,’’ said John C. Green, director of the Ray C. Bliss Institute of Applied Politics at the University of Akron. “Trump doesn’t have to win to reorganize the coalition. If he simply gets a different set of voters than George W. Bush and John McCain attracted, and if it persisted, we could see a reorganization of all of our politics, including the Democratic Party.’’

The Democrats have had their rebellions, too, the last one occurring as the young Hillary Rodham, a onetime “Goldwater Girl,’’ was coming of age politically as an activist student at Wellesley College and later as a law student at Yale. e assault on the party establishment and the effort to reshape the party after Vietnam and the youth rebellions is congruent with the life of another onetime presidential candidate, former senator Gary Hart of Colorado, who was the campaign manager for Senator George S. McGovern of South Dakota in 1972 and later was a reform-oriented presidential candidate in 1984 and in 1988.

The Hart critique has eerie similarities to the current crisis in the Republican Party.

“I don’t think the Democratic Party has ever gotten ahead of the change curve,’’ Hart said in an interview. “We’ve been responding to events more than anticipating them. But so have the Republicans. . . . Trump took over a party that was stagnant and exploited people’s frustrations.’’...