AP offers this report.
UPDATE: The AP story didn’t say who wrote the letter, but Roll Call gives us the names and a taste of the letter:
“‘We hope that you will assure the American people that your Department intends to investigate and prosecute any and all instances of voter registration and other fraud occurring in the days leading up to the election, and that you will enforce all of the federal voting rights laws that are important to preserving the fairness and security of the election process,’ former elections regulator and Justice Department lawyer Hans von Spakovsky wrote on Friday. Former Assistant Attorney General William Bradford Reynolds and former Deputy Assistant Attorneys General Roger Clegg, Michael Carvin and Robert Driscoll also signed the letter.”