For months, Mark Serrano has been one of President Trump’s fiercest defenders and most enthusiastic supporters on TV. In semiregular appearances on the Fox Business Network, the veteran Republican operative has praised Trump’s leadership and bashed news media coverage of him. He’s called Ivanka Trump the most “powerful or influential advocate for women’s empowerment ever in our history.”

Fox News and Fox Business have described Serrano variously as a Republican strategist, a crisis-management expert and a former adviser to President George H.W. Bush since he began appearing on the networks in 2014.

But Serrano has had another role this spring, one that wasn’t disclosed to viewers as he was touting Trump: His firm was a paid consultant to the president’s 2020 reelection campaign.

Federal disclosure forms filed by the Trump committee Saturday show that it paid Serrano’s firm, ProActive Communications, a total of $30,000 for “communications consulting.” The records indicate that it paid $20,000 on April 17 to the company, based in Leesburg, Va., and another $10,000 on May 30.

TV news organizations, including Fox, typically screen would-be pundits and panelists for any financial connection to campaigns, issues or companies they might be asked to comment about on the air. Insiders, such as a campaign official or party strategist, are often welcomed, but only if their professional role is disclosed to viewers upfront.

The disclosures are a matter of transparency; they are supposed to flag a pundit’s potential conflicts of interest and to let viewers know when a commentator has a financial stake that might affect his or her commentary.

Serrano did not reply to multiple requests for comment by email and phone.

People at Fox said Serrano didn’t disclose his connection to the Trump reelection campaign until the latter part of June, two months after his firm and ProActive apparently began working for Trump’s committee.

Serrano subsequently made one appearance on the Fox Business program “Risk & Reward,” during which he was introduced as “Trump’s campaign senior adviser.” He has not appeared on the air since that program aired July 6.

A person familiar with the network’s internal discussions, who wasn’t authorized to speak about them publicly, said Serrano won’t be booked on Fox programs “for the foreseeable future” as a result of the nondisclosure of his work for Trump.

Fox Business issued a statement Monday after reporters inquired about Serrano. It read: “It is the policy of the network to disclose all ties our guests have to any subject matter, and in the case of Mark Serrano, as soon as we were made aware of his new title last month, we made sure to disclose his role during his on-air appearances.”

An official with Trump’s reelection committee said Serrano and his firm were paid for communications strategy, not for his appearances or advocacy on Fox. The official also noted that Serrano’s support for Trump on TV predates his hiring by the reelection committee.

In fact, Serrano has spoken favorably about Trump on Fox and Fox Business from the earliest days of Trump’s presidential campaign.

“You got to remember, Donald Trump has something that none of these other candidates has,” he said in August 2015, according to a transcript of the Fox Business program. “He’s had the experience, on television, these past 12 or 14 years. That is a serious draw for a lot of Americans and that’s why he is more unique than most of these other candidates.”

Since Trump’s inauguration, Serrano has defended him on several issues, including his firing of FBI Director James B. Comey and the various investigations into whether his campaign colluded with the Russian government.

“The only collusion going on in Washington . . . [is] between the media, the Democrats and the deep state, which brings into serious question our national security leaks taking place from the White House,” he said on Fox Business on May 16.

A week later, on the same network, he ripped the news media for their coverage of Trump. “I really don’t even reference it as fake news anymore,” he said. “I consider it E and O news — errors and omissions.”