Sean Hannity is no stranger to crossing the long-held journalistic line about getting too chummy with political candidates, and Fox News has frequently had to pull him back. Last night, Hannity may have spurred new thoughts among executives at the cable-news outlet about the length of his leash.

Hannity and another Fox News Channel opinion host, Jeanine Pirro, both appeared on stage with President Donald Trump Monday night at his final campaign rally in Missouri before Tuesday’s election, a move that in nearly all journalism circles is considered a breach of ethics. Hannity cast aspersions on the journalists covering the event.

Most news organizations actively discourage employees from taking part in political activities, knowing that doing so undermines the ability to provide independent, impartial coverage. The move “feeds into the public perception that Fox isn’t an objective news source,” said Ben Bogardus, an assistant professor of journalism at Quinnipiac University.

“Fox News does not condone any talent participating in campaign events,” the 21st Century Fox-owned cable outlet said in a statement. “This was an unfortunate distraction and has been addressed.” A spokeswoman for 21st Century Fox referred an inquiry to Fox News.

In a statement released on social media, Hannity said “When the POTUS invited me on stage to give a few remarks last night, I was surprised, yet honored by the president’s request. This was NOT planned.” And he said he had not meant to tar any Fox News reporters in the room with the same brush as others.

Hannity rarely purports to be a middle-of-the-road reporter. He’s an opinion host. But other news organizations have reprimanded prominent on-air personalities with not-so-subtle partisan leanings more publicly when they skirted journalistic norms.

In 2010, MSNBC suspended primetime host Keith Olbermann for making donations to political candidates without getting approval from superiors, a violation of company policy at the time. The NBCUniversal-owned network suspended morning host Joe Scarborough that same year for two days without pay after learning the former U.S. Congressman had made eight campaign donations to Florida political candidates.

And in other cases, news outlets have not come down on their anchors. ABC News’ George Stephanopoulos was criticized in 2015 when it was revealed he had made donations totaling $75,000 to the Clinton Foundation. The Disney network did not mete out any sort of punishment.

Fox News has long had to grapple with Hannity’s antics. Hannity in 2016 appeared in a promotional video for the Trump campaign, but Fox News at the time issued a statement saying that executives had not been aware of it, noting he would not appear in any more through the remainder of the election. In 2010, Fox News ordered him not to broadcast his program as part of a Tea Party rally originating from Cincinnati. In April of this year, it was revealed Hannity had tapped former Trump attorney Michael Cohen for legal advice even though he routinely offered opinion on both the President and news events involving Cohen. “Michael Cohen has never represented me in any matter,” Hannity said at the time. “I never retained him, received an invoice, or paid legal fees. I have occasionally had brief discussions with him about legal questions about which I wanted his input and perspective.”

Coming down harder on Hannity could provoke the ire of the Fox News faithful. Hannity is one of the last links to Fox News’ origins. He has had a perch on the network’s primetime schedule since Rupert Murdoch launched the outlet in 1996 – first with liberal co-host Alan Colmes, and then solo. His program, “Hannity,” has been the most-watched program in cable-news for seven consecutive months – trumping his main competitors, Rachel Maddow and Chris Cuomo in one of the medium’s most competitive time slots.

Fox News sets its primetime schedule – shows led by Tucker Carlson, Hannity and Laura Ingraham – apart from its news programs, and that may shield Hannity from some of the criticism he often generates, says Bogardus, the journalism professor. “It may look bad, but for someone who is talking about opinion versus journalism, it’s really something that should be expected,” he says.

The question for Fox News executives is whether Hannity’s incidents tarnish other parts of the business – and, perhaps, whether those pieces are as valuable as the real estate the primetime host commands. Fox News news personnel like Bret Baier, Shepard Smith and Chris Wallace don’t snare as much daily audience as their colleague, and have to toe a straighter line. “When things like this happen, it reinforces a view which their newspeople may not hold” says Bogardus, and hurts the concept that Fox News is, as it once portrayed itself, “fair and balanced.”