Here's something you may not have noticed. Most of the other GOP candidates for president who have fallen by the wayside have, so far, failed to endorse Mitt Romney.

Michelle Bachmann, Rick Santorum and Newt Gingrich have not thrown their support behind Romney. The New York Times reports that many in Washington are wondering what the three are trying to accomplish with their reluctance.

Some speculation revolves around whether Mitt Romney will help them pay off their debt from their failed campaigns. Then again, some may be nursing hurt feelings.

Of all the reasons for not endorsing Mr. Romney, the strongest may be the simplest. After months of criticizing Mr. Romney as the weakest possible Republican nominee, the defeated candidates are perhaps just struggling to get out the warm words.

That is surely the case with Mr. Santorum, whose bitter fight with Mr. Romney in the waning weeks of the primary season seemed to leave him with a particularly bad taste in his mouth.

Asked by Piers Morgan of CNN last week whether he was endorsing Mr. Romney, Mr. Santorum, bottom, danced around the question.

“You can call it whatever you want,” Mr. Santorum said, adding a minute later that Mr. Romney “is going to be the Republican nominee.”

“I’m going to be for the Republican nominee,” he said. “We’re going to do what we can to beat Barack Obama.”