Indeed, the phenomenon goes back at least to 1976, when the Democrats watched peanut farmer Jimmy Carter plod inexorably to their presidential nomination, and then were besieged with doubt about whether they had picked a loser. As luck, the Watergate hangover and Mr. Carter's grim determination turned out, they were mistaken. Those doubts, however, were validated four years later when he was denied re-election.
This year, well before the Republicans have nominated their standard-bearer, buyer's remorse already appears to be setting in about their apparent but not inevitable front-runner, Mitt Romney. As an original seven-candidate field has been winnowed down to four, Mr. Romney appears likely to be the ultimate GOP survivor, but with little enthusiasm among the party faithful.
The doubts are based on two questions: Can he win, and is he one of us? The first query dominated the early phase of the campaign, driven by the overwhelming desire to beat President Obama. But Mr. Romney's uneven at best performance in debates and on the stump has fed a growing impression that the man from Massachusetts by way of Michigan may not be up to the task.
As long as Mr. Romney and his strong business background seemed to be the ticket for making Mr. Obama a one-term president, whether he was a "true conservative" was something that may have troubled some of the faithful, but it didn't appear to be an insurmountable barrier to his nomination.
As doubts about his electability festered, though, his ideological purity or lack thereof rose to the fore. The doubts were mightily encouraged by the four most conservative competitors -- Michele Bachmann, Rick Perry, and the surviving Newt Gingrich and Rick Santorum.
The competition among these four for the anybody-but-Romney mantle served his cause in dividing his opposition. As the field narrowed, however, the argument sharpened and focused that he was not "one of us." Heavy television attacks on Mr. Gingrich, whose vulnerabilities were well known, took their toll on him, allowing Mr. Santorum, the mystery man in the field, to play the "true conservative" card effectively as Mr. Gingrich stumbled.
Suddenly, Republicans following the drama were faced with deciding which of the survivors represented the party as it has become, with the vanishing of liberals, the diminution of moderate sentiment and the infusion of the tea party. The other surviving candidate, Ron Paul, qualified on social and economic grounds but clearly not on foreign policy.
So Mr. Romney has spent the last year or more trying to convince the party's conservative base that he belongs. Instead, he has created concern not only about his electability but also about whether he is a mere ideological chameleon, not to be trusted to adhere to "true conservative" dogma.
Buyer's remorse usually sets in after the nomination is nailed down. But this time around, the early aura of inevitability that Mr. Romney and his money would sew it up has already been shaken by the first caucus and primary results. A substantial segment of the party seems to be saying: Save us somehow from the fate in store for us if Mitt Romney is our nominee.
With Mr. Gingrich and his characteristic bravado continuing to self-destruct, Mr. Santorum seems an unlikely savior, but his record certainly qualifies as a pure conservative of the sort the party has become across the board. As the GOP lurches ever rightward, the ultimate remorse may be about lurching too far, and alienating the moderate center where elections usually are decided.
It will be ironic if Mr. Romney, in laboring to go with that flow to win party acceptance, damages what reputation he still has as a man of moderation, capable of winning the independent voters any Republican nominee will need in order to be elected in the fall.
Jules Witcover is a syndicated columnist and former long-time writer for The Baltimore Sun. His latest book is "Joe Biden: A Life of Trial and Redemption" (William Morrow). His email is email@example.com.