And that responsibility gives Fox News an oddly bipolar feel these days. Long, detailed interviews with candidates and considered discussions of the pricklier primary issues like immigration and Medicare are woven into the cable channel’s customary brisk, blistering brio and hyperbole — all those flashy news alerts about President Obama waging “class warfare,” updates on an elderly robbery suspect known as the Geezer Bandit and the liberals’ “war on Christmas.”

Actually, not even the 2012 campaign can crimp the cherished Fox News holiday tradition of mixing persecution and poinsettia. This week, a Fox News reporter stopped Gov. Lincoln Chafee of Rhode Island, an independent, demanding to know why he used the word “holiday tree” instead of “Christmas tree” in a lighting ceremony invitation. Mr. Chafee, who looked at the camera with the pleading congeniality of a Soviet dissident stopped by the K.G.B., tried to explain the separation of church and state and noted that he had used the same neutral wording as his Republican predecessors, to no avail. “What holiday is it?” the reporter asked as Governor Chafee walked away. “What holiday is it, Governor?” (Even Jon Stewart’s mockery doesn’t seem to dim the channel’s ire.)

Fox News is known for ambush interviews, but it doesn’t have to lie in wait for Republican candidates. Many news organizations took a telling clip from a recent interview that Mitt Romney gave to the Fox News anchor Bret Baier in Florida that showed the usually imperturbable former Massachusetts governor looking rattled and jumpy when asked about health care. The full interview was long, thorough and even more tense — Mr. Baier also pressed Mr. Romney on his changing views on amnesty for illegal immigrants with the polite insistence that candidates used to face from single-issue voters in Iowa kaffeeklatsches.

Mr. Romney wasn’t happy with the interview, but Fox News viewers don’t seem thrilled with him either. Nearly half of them said they would vote for Newt Gingrich if the state’s Republican presidential caucus were held today; only 12 percent said they favored Mr. Romney.

That could be because Mr. Gingrich is a much more familiar face on Fox News, having logged more than 50 appearances since the campaign began. Mr. Romney is playing catch-up, seizing every opportunity to appear on the channel. He took a break from a forum in Washington sponsored by the Jewish Republican Coalition to tell a Fox reporter that Newt Gingrich is for amnesty for illegal immigrants and against child labor laws, among other things. “The list will go on and on as we get a clear indication of exactly where the speaker stands,” Mr. Romney said, not cheerfully.