Well before he was elected as House speaker, Rep. Mike Johnson, R-La., played a key role in efforts by then-President Donald Trump and his allies to overturn Joe Biden's electoral victory in the 2020 election.

Johnson, who served as the GOP caucus vice chair and is an ally of Trump, led the amicus brief signed by more than 100 House Republicans in support of a Texas lawsuit seeking to invalidate the 2020 election results in four swing states won by Biden: Georgia, Michigan, Pennsylvania and Wisconsin.

The lawsuit, filed by Texas Attorney General Ken Paxton, a Republican, called on the Supreme Court to delay the electoral vote in the four states in order for investigations on voting issues to continue amid Trump's refusal to concede his loss. It alleged that the four states changed voting rules without their legislatures' express approval before the 2020 election.

Johnson at the time sought support from his GOP colleagues for the lawsuit, sending them an email with the subject line "Time-sensitive request from President Trump."

"President Trump called me this morning to express his great appreciation for our effort to file an amicus brief in the Texas case on behalf of concerned Members of Congress," Johnson wrote in the December 2020 email, which was obtained by NBC News.

"He specifically asked me to contact all Republican Members of the House and Senate today and request that all join on to our brief," he continued. "He said he will be anxiously awaiting the final list to review."