Ed Kilgore fears it:
I certainly don't think [Trump is] in any danger of winning the nomination. But the real issue is that if he maintains or increases these levels of popularity among rank-and-file Republicans, the tolerance of GOP insiders for lower levels of craziness is bound to increase, giving them exactly what they do not need right now: another big push to the right.
Rich Lowry thinks Trump's run "is all an elaborate put-on," or at least he hopes it is:
Trump says he’d wage war [in Libya] only to take the country’s oil. And he’d take Iraq’s oil, too. Obama is groping for a doctrine in the Middle East. Trump already has one: Steal its oil. In Trump, Noam Chomsky will finally have met a Western imperialist truly bent on expropriating the Third World’s wealth.
Ben Smith and Maggie Haberman reported out the story:
[W]hile he is “serious” from the organizational point of view and appears very likely to emerge as a formal candidate for office, he will struggle hard to be taken seriously as a potential Republican nominee. Trump may not be in on the joke — he rarely jokes about himself — but he has been a punch line as long as he’s been a public figure. He’s still more of a sideshow than anything else, most Republican insiders are convinced, and his respectable showings in largely meaningless early polls reflect little more than his widespread notoriety.
Chait likewise doesn't buy Trump as a viable candidate:
Trump as a GOP candidate represents the easiest oppo hit in the history of primary races. He has advocated single-payer health care and called George W. Bush "evil."
The Dish 