Former Trump campaign chairman Paul Manafort’s indictment could give special counsel Robert Mueller leverage over Manafort to help him put President Trump in legal jeopardy, a veteran House Republican worried Monday.

“That’s obviously the plan here, in my judgment,” Rep. Trent Franks, R-Ariz., told a Phoenix radio host on Monday morning.

Manafort and business partner Rick Gates surrendered to the FBI on Monday; they face charges related to money laundering and failing to register as foreign agents, after years of working on behalf of pro-Russian Ukrainian politicians. President Trump countered that the crimes were allegedly committed before the pair joined his campaign, but Franks sees danger anyway.

“They’ll threaten Manafort in every way that they can,” Franks said on KTAR radio. “They’ll try to say ‘Well, listen. We’re not really after you, we’re going to try to manufacture something against Donald Trump no matter what, and if you can help us, it would sure go well for you.’ And I think we need to be prepared for that.”

A third Trump campaign official is already cooperating with the Mueller probe, after pleading guilty to lying to the FBI about his contacts with Russian-linked officials during the campaign. Former foreign policy adviser George Papadopoulos lied about his meetings with a professor who had “substantial connections to Russian government officials,” who told Papadopoulos that Russia had “thousands of emails” stolen from Hillary Clinton’s team, according to court documents.

Franks has maintained for months, however, that Mueller has a conflict of interest stemming from his longstanding friendship with former FBI Director James Comey. Trump fired Comey in part due to frustration over the Russia investigation, a decision that led to the appointment of Mueller, who led the FBI before Comey.

“I believe that Mr. Mueller’s conflict of interest is absolutely incontrovertible, and I think this is further indication he’s headed in this direction no matter what,” Franks said. “It’s ironic because ostensibly his investigation is supposed to be into Donald Trump’s potential involvement with Russia, yet this doesn’t have anything to do with Donald Trump.”

The lawmaker argued that Mueller should investigate a bribery case involving a Russian company that purchased a majority stake in a Canadian company that owns a major American uranium mine. “The same month that deal went down . . . Bill Clinton gets a half a million dollars speaking engagements from the Russians and of course Hillary Clinton’s foundation gets almost $2.5 million from them as well,” Franks said according to a transcript released by his office.

The recent outcry over the uranium deal stoked Democratic concerns that Trump might plan to fire Mueller, who led the FBI at the time the agency was investigating bribery charges pertaining to Russian investment in the U.S. nuclear industry.

“The president must not, under any circumstances, interfere with the special counsel’s work in any way,” Senate Minority Leader Chuck Schumer, D-N.Y., said Monday. “If he does so, Congress must respond swiftly, unequivocally, and in a bipartisan way to ensure that the investigation continues.”