Jim Acosta, the square-jawed CNN correspondent, has stood out among the White House press corps for his impassioned on-air monologues about the importance of the First Amendment.

During a tense White House briefing on Thursday, he challenged the press secretary, Sarah Huckabee Sanders, to disavow President Trump’s description of journalists as “the enemy of the people.” Ms. Sanders declined to do so, saying she had been personally attacked in the media and had faced threats since starting her job.

Opinions on the exchange varied.

Many liberals praised Mr. Acosta for confronting Ms. Sanders, particularly after he had faced vitriol from Trump supporters at a Florida rally on Tuesday. Many conservatives knocked Mr. Acosta as a biased showboat. And some of his rival White House reporters rolled their eyes.

Mr. Acosta, a CNN veteran, is used to it.

Since last January, when the president-elect shouted him down at a news conference, Mr. Acosta, 47, has been a featured player in the Trump v. Media battle royale. The president, no fan of CNN, has called Mr. Acosta “a real beauty” and refused to take his questions last month during a session with reporters in Britain.