“A lot of work to do,” said Kate O’Beirne, a veteran conservative commentator. Pete Wehner, who was an aide to President George W. Bush, fears that Republican gains expected in the midterm elections this fall will offer another “false dawn,” as they did in 2010.

But the Democrats’ experience showed that party overhauls could be halting, unpredictable and subject to rapid shifts in circumstance. Democrats glimpsed false dawns themselves while losing five of six presidential elections beginning in 1968: They held the House throughout and gained seats in every midterm election after a Republican presidential win.

Republicans are contemplating tinkering with their nomination process, something Democrats tried with little success. The Democrats’ 1988 “Super Tuesday” primaries, designed to provide an opening for an electable Southern moderate, instead made winners out of Michael Dukakis and Jesse Jackson.