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.
The ouster of Representative Marjorie Taylor Greene from the ultraconservative group and the rise of another rebel faction have raised questions about where the real power lies on the far right.
The group’s proposals have no chance of passage, but they have further mired the military spending bill in a partisan fight and highlighted Republican divisions over the war.
The bipartisan group will challenge hard-right House Republicans in their home districts, running ads that accuse the lawmakers of holding antidemocratic positions.