Nevada Sen. John Ensign will announce his intention to resign Friday, Roll Call's Shira Toeplitz reports. Ensign had already said he would not seek reelection next year. The Republican has been battered by controversy since he admitted to having an extramarital affair with his staffer's wife. Ensign tried to hide the affair before coming clean in 2009; his parents had given the staffer's family a gift of $96,000 a year earlier.

The aide in question, Douglas Hampton, was indicted by federal prosecutors last month for lobbying Ensign's office in violation of Congress' rules requiring a "cooling off" period before staffers can lobby their old colleagues. Prosecutors said in December that they did not plan to charge Ensign with helping Hampton get the lobbying gig.