The onetime Trump supporter was driven into hiding after Fox News and prominent Republicans spread a false narrative that he was a government agent who helped instigate the attack on the Capitol.
The roughly 1,700 messages are from the cellphone of Representative Scott Perry, who was involved in discussions with Trump administration officials about overturning the election.
Prosecutors said he had never worked as an agent of the government, again refuting a right-wing theory that he helped instigate the Capitol riot in a federal plot to discredit Trump supporters.
Federal prosecutors described the shift in a court filing that highlighted conflicts of interest in the overlapping legal representation of witnesses and defendants in the case.
The appeal seeks to narrow the scope of testimony that former Vice President Mike Pence can provide the grand jury investigating former President Donald Trump’s efforts to stay in power.