The bottom three finishers in South Carolina's GOP presidential primary should drop out of the race and allow their supporters to coalesce behind Sens. Ted Cruz and Marco Rubio, Fox News pundit Charles Krauthammer said Saturday night.With businessmanwin in a row, a winnowing of the field is needed to make for a three-man race, Krauthammer said during Fox post-primary coverage.Former Florida Gov. Jeb Bush and neurosurgeon Ben Carson are the two most likely to take his advice, Krauthammer admitted, while Ohio Gov. John Kasich has indicated he will stay in the race, though Krauthammer doesn't see him having a major effect.Polls have shown few people naming Trump their second choice, and with Trump carrying about one third of the vote, a split between Cruz and Rubio for the remaining voters would make the race a true contest, Krauthammer said.The most likely candidate to drop out first is Bush, Krauthammer said, who likely would see it as a case of noblesse oblige."He obviously thinks that Trump would be a disaster for the party," and his sense of honor and tradition will compel him to drop out to help defeat Trump, Krauthammer said.Bush suspended his campaign shortly after Krauthammer's comments.Panic has likely set in on the so-called GOP "establishment," Krauthammer added, and Rubio's "hiccup" in New Hampshire did nothing to help."The panic ought to be there right now," he said. "If you don't have the field to three I don't see how Trump is stopped."