Media coverage of former Special Counsel Robert Mueller's upcoming testimony on Capitol Hill will "dwarf" that of past congressional hearings linked to the Russia investigation, Fox News' Capitol Hill senior producer Chad Pergram predicted Tuesday.

"We've had some explosive hearings on Capitol Hill before," Pergram said on "Hannity." "You think of James Comey testifying, Jeff Sessions in the Senate a couple of years ago. You think about Michael Cohen in February. This will dwarf that. The pure magnitude of this will be off the Richter scale."

Pergram also broke down the events that led to Mueller's scheduled July 17 appearances before both the House judiciary and intelligence committees.

ROBERT MUELLER AGREES TO TESTIFY BEFORE HOUSE LAWMAKERS JULY 17 AFTER SUBPOENA, NADLER AND SCHIFF ANNOUNCE

"I'm told Bob Mueller would only appear if he was subpoenaed, and will stick to the 'four corners' of his report. That is what he said in a statement several weeks ago when they released the report. Of course, you can imagine Democrats wanting to get at him and see if there was distance between him and William Barr, the attorney general," Pergram said, describing the subpoenas as "friendly."

Pergram also predicted the probable line of questioning from House Republicans.

"They want to know the genesis of the Steele dossier, the [Lisa] Page and [Peter] Strzok text messages, one source said to me tonight, a Republican source. How many informants were on the campaign, and what were they looking at?" Pergram said.

Pergram also noted that if Mueller doesn't adequately answer Republicans' questions, they may say he is "not very credible."

CLICK HERE TO GET THE FOX NEWS APP

He also revealed the reasoning behind Nadler and Schiff arranging the testimony.

"They said "Americans have demanded to hear directly from the special counsel so they can understand what he and his team examined," and that is why they want him to appear. That's very key," Pergram said.