If Newt Gingrich won South Carolina because of one of his most indefensible ideas -- ending child labor laws so that poor kids can become janitors in their own schools -- it's interesting that he's being killed in Florida over one of his most defensible ones: space exploration.

Last week, Gingrich said that by the end of his second term, America would build a colony on the moon. Mitt Romney's campaign has been gleefully attacking him on his "grandiose" lunar ambitions ever since (sample press release: "EARTH TO NEWT..."). "Do we have to wait to do the obituary on Newt's candidacy?" Slate's Jacob Weisberg tweeted. "I think moon colony killed it. Neat encapsulation of his vanity/insanity." Public Policy Polling's Tom Jensen points out that Florida voters oppose the Moon plan by 52 percent to 22 percent -- and only 34 percent of Gingrich's own voters like the idea. "I doubt this issue really has much to do with Newt's collapse in Florida but I don't think it's helping him either," Jensen writes.

Romney is clearly enjoying the chance to argue that Gingrich as a maniac with delusions of grandeur. That argument is not without evidence. However, going back to the moon is not a terrible idea! While a lunar colony is a tough sell politically, The New York Times' Kenneth Change reports, it's doable technologically: 

“It’s not something that should be mocked or should be seen as a remote possibility,” said Michael Gold, director of the Washington office of Bigelow Aerospace, a private space company. “The reason this is both possible and economically viable is that many of the systems and technology, if not all, already exist.” ...

Charles Miller, formerly a senior adviser at NASA for commercial space, said all of the pieces of Mr. Gingrich’s space plans were plausible if not fleshed out. “The improbable thing at this point is if Newt will become president,” he said.

Gingrich has taken a lot of positions that are tough to defend, like attacking Romney for paying a low federal tax rate when Gingrich's own tax plan would lower that rate to nearly zero. His remarks about President Obama being a "food stamp president" and that poor kids have no work ethic play on ancient racial stereotypes. He once complained about an Israeli "land grab," Salon notes, and now he's calling the Palestinians "an invented people." He came out for banning all embryonic stem cell research this weekend, which he once supported, as The Washington Post's Karen Tumulty points out. So it's a little sad that one issue on which Gingrich has been consistent for years and which has brought us great things -- Tang, velcro, satellite TV, a lot of essays on space sex, summer space camp -- looks like the one thing that destroys his candidacy.