U.S. Attorney John Durham is reviewing "three important things" in his investigation into the origins of the Russia investigation, according to an appraisal by former Rep. Trey Gowdy.

The South Carolina Republican gave his best-guess assessment of the secretive "investigation into the investigators" Sunday on Fox News, where he is a contributor.

"He's looking at three things — the factual predicate for this Russia investigation. And I'm not talking about the summer of 2016. I'm talking about stuff that happened in late 2015 and early 2016," Gowdy told Sunday Morning Futures host Maria Bartiromo.

"Remember, the DOJ and the FBI told Paul Ryan and Devin Nunes and myself repeatedly and exclusively that nothing happened before June of 2016. No payments were made, no contacts with the Trump campaign," he added, referring back to his time as a lead GOP investigator in Congress. "I'm sure John Durham is looking to see whether or not that's true."

Two other areas of interest Gowdy pointed out were alleged government surveillance abuses in targeting a member of the Trump 2016 campaign and the January 2017 intelligence assessment on Russian election interference.

"He's also looking at the FISA process and misrepresentations made to the FISA court," the former federal prosecutor said. "I think he's also looking at that ICA, that intelligence community assessment, that John Brennan got done towards the end of the Barack Obama tenure, to make sure whether or not that was thoroughly investigated and whether or not all the right information made its way into that ICA."

Durham was assigned to the task by Attorney General William Barr, who said last spring "some of the facts" about the Russia investigation "don't hang together with the official explanations of what happened." Democrats have criticized the review, which transitioned into a criminal investigation in the fall, as politically motivated scheme to undermine the work of former special counsel Robert Mueller and attack President Trump's perceived enemies.

According to a New York Times report last week, Durham is reviewing former CIA Director John Brennan’s analysis of Russian election interference, including scrutiny of the former Obama CIA director’s handling of a secret source said to be close to the Kremlin. The Connecticut prosecutor is also scrutinizing the intelligence community’s interagency turf war over viewing secretive foreign intelligence and the government restricting access to Obama's emails that were hacked by Russians but obtained by a foreign ally.

Presented with a counterintelligence activity timeline covering late 2015 and early 2016, ensnaring people who would become members of Trump's campaign, Gowdy said officials have some explaining to do because, he stressed, the Justice Department and FBI repeatedly told lawmakers "nothing happened with respect to the Trump campaign before June of 2016."

"If something did happen, then either the FBI misrepresented facts to us, or it wasn't the FBI, it was another agency that was doing it. Both of those are important to know. And John Durham, I hope, is going to be able to answer that question," Gowdy said.