For the first time in its 20-year history, Fox News is stumbling. Roger Ailes, its founder and guiding force, has been driven out by embarrassing revelations of repeated sexual harassment. The newsroom is sharply divided, some long-term contributors are leaving, and the channel’s parent company has started the expensive process of settling with Mr. Ailes’s accusers.

This might sound like bad news for the Republican Party, which has tied itself to the network for years. But Fox News has long been a double-edged sword for Republicans, and perhaps nothing illustrates that contradiction quite like the rise of Donald J. Trump.

Fox News can be a virtual kingmaker leading up to the primaries, providing candidates with a platform, firepower for their arguments — including Mr. Trump’s long-held assertion, which he rejected only on Friday, that President Obama was not born in the United States — and a large, receptive audience. But it also boxes in candidates with the narrow, cosseted views of its audience, making it almost impossible to reach out to more moderate Republicans during the general election.

Now some conservative intellectuals, such as The Wall Street Journal’s Bret Stephens and the Wisconsin radio talk show host Charlie Sykes and others, are asking whether Fox is a net plus or minus for their movement. They wonder what good it accomplishes when it leads to the nominations of Republicans like Mr. Trump, who have a low chance of winning a general election.