Nearly half of the Fox News watchers said they would vote for Mr. Gingrich if the state’s Republican presidential caucus were held today. Just 12 percent of the regular Fox watchers said that Mr. Romney, the former governor of Massachusetts, is their choice to be the Republican standard-bearer.

The gap between the two men among Fox watchers is nearly twice as large as it is among likely Republican caucusgoers in Iowa. Mr. Gingrich — who was a Fox News analyst before beginning his presidential campaign — leads Mr. Romney 31 to 18 percent among Republican voters in the state over all, the poll found…

Mr. Gingrich, by contrast, often seems more at ease on Fox than his rivals, including Mr. Romney. As he attempts to ride his new-found momentum, Mr. Gingrich is likely to draw on his experience as a Fox analyst — and years of appearances on news programs.