Frank Schubert, political director for the National Organization for Marriage (NOM), has called Newt Gingrich's recent shift on gay marriage “stupid.”

Gingrich, the former House Speaker and a leading candidate for the 2012 GOP presidential nomination, told The Huffington Post last week that he's prepared to accept “a legal document issued by the state” for gay and lesbian couples.

Gingrich added that momentum is on the side of supporters and that he fears the issue could hurt the Republican Party, whose official platform opposes the legalization of marriage equality.

(Related: Newt Gingrich says it's time to accept the reality of gay marriage.)

Schubert – who has managed campaigns for NOM since 2008's Proposition 8 in California – criticized Gingrich in a blog post.

“[S]ometimes good men say stupid things, and this is one of those times,” Schubert wrote.

“Gingrich's conclusion that gay 'marriage' is inevitable is ridiculous. His comments suggest the results of marriage races in Maine, Maryland and Washington, which allowed three deep-blue states to endorse redefining marriage means that it is inevitable. I wonder if the Speaker also thinks that the Republican Party is doomed and can never again win a national election. After all, marriage performed, on average, 6.6 points better than did the Republican ticket in these very Democratic states.”

“Yes, we are disappointed with the election results, but let us not overstate their importance. By an overwhelming 60% margin (according to a national survey conducted by Gingrich's own pollster, Kellyanne Conway), the American people continue to believe that marriage is the union of one man and one woman.”

“Gay 'marriage' is no more inevitable than is permanent Democratic control of the White House,” he added.