The wireless carrier said that it was working with the F.B.I. and the Secret Service to investigate a recent wave of fraudulent messages, but said the source did not appear to be Russian hackers.
The House committee is reaching out to the wife of Justice Clarence Thomas after public disclosure of text messages documenting her support for President Donald J. Trump’s efforts to overturn the election.
The messages between Ms. Thomas and Mark Meadows are the first evidence that she directly advised the White House in efforts to reverse the election results.