So will Newt Gingrich suffer the same fate? Not necessarily.

Many observers seem surprised that Mr. Gingrich’s, well, colorful personal history isn’t causing him more problems, but they shouldn’t be. If hypocrisy is the tribute vice pays to virtue, conservatives often seem inclined to accept that tribute, voting for candidates who publicly espouse conservative moral principles whatever their personal behavior. Did I mention that David Vitter is still in the Senate?

And Mr. Gingrich has some advantages none of the previous challengers had. He is by no means the deep thinker he imagines himself to be, but he’s a glib speaker, even when he has no idea what he’s talking about. And my sense is that he’s also very good at doublethink — that even when he knows what he’s saying isn’t true, he manages to believe it while he’s saying it. So he may not implode like his predecessors.

The larger point, however, is that whoever finally gets the Republican nomination will be a deeply flawed candidate. And these flaws won’t be an accident, the result of bad luck regarding who chose to make a run this time around; the fact that the party is committed to demonstrably false beliefs means that only fakers or the befuddled can get through the selection process.

Of course, given the terrible economic picture and the tendency of voters to blame whoever holds the White House for bad times, even a deeply flawed G.O.P. nominee might very well win the presidency. But then what?

The Washington Post quotes an unnamed Republican adviser who compared what happened to Mr. Cain, when he suddenly found himself leading in the polls, to the proverbial tale of the dog who had better not catch that car he’s chasing. “Something great and awful happened, the dog caught the car. And of course, dogs don’t know how to drive cars. So he had no idea what to do with it.”

The same metaphor, it seems to me, might apply to the G.O.P. pursuit of the White House next year. If the dog actually catches the car — the actual job of running the U.S. government — it will have no idea what to do, because the realities of government in the 21st century bear no resemblance to the mythology all ambitious Republican politicians must pretend to believe. And what will happen then?