Rep. Devin Nunes, R-Calif., believes he has found the definition of the "insurance policy."

A text message sent by former FBI agent Peter Strzok to Lisa Page, a former FBI lawyer with whom Strzok was having an affair, in August 2016 that mentioned an "insurance policy" has long been a subject of concern among Republican investigators who believe there could have been a plot to undermine then-candidate Donald Trump.

In an interview Tuesday with Fox News, Nunes tied the "insurance policy" text to the FBI's use of an unverified dossier compiled by British ex-spy Christopher Steele to obtain Foreign Intelligence Surveillance Act warrants to wiretap Trump campaign adviser Carter Page.

"We believe that insurance policy is not just about investigating the Trump campaign," Nunes said. "We believe it's to ensure that they were able to get the FISA warrant on Carter Page so they could go in and look at the emails in the campaign."

Although the initial FISA application in October 2016 was marked as being a "verified application," FBI officials later acknowledged that the dossier's claims were not confirmed. In public testimony after he was fired in May 2017, former FBI Director James Comey called at least some of the dossier's allegations "salacious and unverified."

Last year Comey was challenged about the dossier's use in the FISA warrants in an interview with Fox News. "My recollection was, it was part of a broader mosaic of facts that were laid before the FISA judge to obtain a FISA warrant," he said.

With Comey's "mosaic" in mind, Nunes said the evidence that sought to corroborate the dossier was equally as troubling.

"On the FISA application, remember, you have Comey who has called this a mosaic. So Comey's mosaic," Nunes said. "Remember when we came out with our memo that brought forward the fact that they had used the Clinton-paid-for dossier, the dirt, opposition research, and then they leaked that to press outlets and then they picked up those press reports and used it in the FISA application. Comey said, 'Oh, no no it was a mosaic, there was so much more information there.' Well there is more information there that we think is equally as bad as using opposition research."

A February 2018 memo from the House Intelligence Committee, then led by Nunes, alleged Steele was paid over $160,000 by the Democratic National Committee and Hillary Clinton's campaign through the Perkins Coie law firm and opposition research group Fusion GPS to "obtain derogatory information on Donald Trump's ties to Russia." The memo also said the FBI never informed the Foreign Intelligence Surveillance Court of the dossier's Democratic benefactors or Steele's anti-Trump bias when it applied to spy on Page, who was investigated by special counsel Robert Mueller over his interactions with Russians but was never charged.

In a rebuttal to the House Intelligence GOP memo, Democrats argued the Justice Department and FBI "met the rigor, transparency, and evidentiary basis needed to meet FISA's probable cause requirement."

Carter Page was subject to the FISA warrant in October 2016, after he left the Trump campaign. Three renewals followed, stemming into 2017. The FISA documents were released with heavy redactions in July 2018.

Text messages between Strzok and Lisa Page, in which they displayed a negative opinion of Trump, were uncovered over the course of the Justice Department's inspector general investigation into the DOJ and FBI's conduct during the investigation into Hillary Clinton's unauthorized private email server, which she used while serving as secretary of state.

The text Strzok sent to Lisa Page on Aug. 15, 2016, read: “I want to believe the path you threw out in [former FBI Deputy Director Andrew McCabe's] office — that there’s no way he gets elected — but I’m afraid we can’t take the risk. It’s like an insurance policy in the unlikely event you die before you’re 40.”

Both Strzok and Lisa Page, who are no longer with the FBI, were grilled about it during testimony to a joint congressional task force looking into potential bias within the Justice Department and FBI.

Strzok testified to Congress that the mid-August 2016 text was part of a larger conversation about protecting an "extremely sensitive source" as he and Page considered how far to lean into the counterintelligence investigation into possible links between the Trump campaign and Russia, as they didn't think Trump had a very good chance of beating Hillary Clinton in the election. Page admitted the texts were referring to the Russia investigation but said it was a "continuing check-in" to decide how quickly to proceed with the investigation based on the outcome of the election.

Justice Department Inspector General Michael Horowitz is looking into alleged FISA abuse and is expected to wrap up his investigation in late May or June. U.S. Attorney John Huber of Utah is also looking at potential misconduct by federal officials. On top of all that, this week it was revealed Attorney General William Barr tasked U.S. Attorney John Durham to review the origins of the Russia investigation.

Comey and former FBI General Counsel James Baker have said they are confident the bureau did nothing wrong in obtaining the warrants, although Baker admitted the DOJ inspector general's FISA abuse investigation will find "mistakes."