But in a court filing and in text messages obtained by CNN, new pieces of evidence have emerged in recent days fleshing out the degree of their involvement with the Trump White House in strategy sessions, at least one of which included discussions about encouraging Mr. Trump’s supporters to march to the Capitol on Jan. 6, despite warnings of potential violence. Some continued to push to try to keep Mr. Trump in office even after a mob of his supporters attacked the complex.

“In our private chat with only Members, several are saying the only way to save our Republic is for Trump to call for Marshall law,” Representative Majorie Taylor Greene, Republican of Georgia, wrote to Mr. Meadows on Jan. 17, 2021, misspelling the word “martial.”

The revelations underscore how integrated Mr. Trump’s most fervent allies in Congress were into the effort to overturn the election on several fronts, including a scheme to appoint pro-Trump electors from states won by Mr. Biden — even after they were told such a plan was unlawful — and how they strategized to pressure their fellow lawmakers to go along.