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In a 2011 letter, Kelner touted the firm’s election and political law practice as one of the oldest in the country. “Our election and political law clients include some of the nation’s leading trade associations, financial institutions, manufacturers, and technology companies,” Kelner said then.

Federal election records show Kelner contributed to Mitt Romney’s presidential campaign in 2012. Kelner’s law firm bio said his clients include the Republican National Committee and the National Republican Congressional Committee.

Kelner represented John Lopez, the chief of staff to former U.S. Sen. John Ensign, in a Senate Ethics Committee and Justice Department investigation into the senator’s efforts to contain the fallout from an affair he had with another aide’s wife. Lopez received immunity before becoming a key witness in the case against Ensign, who resigned amid the investigation. Kelner later represented former U.S. Rep. Tom Petri in a House ethics investigation into his advocacy for two Wisconsin companies in which he held stock. He was ultimately cleared.

Lawyers who know Kelner, a Covington lawyer since 1998, praised his prowess.

“I can attest Rob is a first rate criminal defense lawyer. He was also #NeverTrump. Very principled guy,” Perkins Coie election-law partner Marc Elias, general counsel for Hillary Clinton’s presidential campaign, wrote in one tweet Thursday night. Elias said in another: “Rob Kelner is a very good lawyer who knows when a client needs immunity. And if Rob says Flynn has a ‘story to tell’, WH should watch out.”

Elias also said on Twitter that Flynn “wisely chose a lawyer who owes nothing to the Trump WH. Rob will provide independent counsel to a guy with ‘a story to tell.’”

Michael Bopp, a Gibson, Dunn & Crutcher partner who specializes in congressional investigations, said it is common for witnesses to request immunity in exchange for their testimony. Bopp described Flynn’s offer as a “clever and tactically-smart move.”

“It shifts the focus from him taking the fifth to, ‘Hey, could he actually get the immunity?’ People are now thinking and talking about that. That’s smart. That’s tactically a good move,” Bopp said. “But it’s not saying a lot saying, ‘Hey, I’ll testify if I’m immunized.’”

If immunized, Flynn could testify more comfortably rather than mince his words, Bopp said. With the House, Senate and Justice Department all conducting their own investigations, that comfort level could reduce Flynn’s risk of providing one panel with slightly different testimony and being accused of obstructing the investigation.

“What you often have are referrals made (to the Justice Department) for false statements or obstructing a congressional investigation. Even those allegations themselves can be devastating to a person’s reputation,” Bopp said. “It could take time and money to defend.”