Freshman Rep. Eric Massa (D-N.Y.) is expected to announce on a 3:30 p.m. conference call that he will not run for a second term in November.
A source who has spoken to Massa said the Congressman will announce he is leaving because of a recurrence of cancer. Massas retirement was first reported by the New York Daily News on Wednesday afternoon.
Massa was first elected in 2008, when he defeated then-Rep. Randy Kuhl in the Republican-leaning 29th district.
Republicans had been targeting Massa for defeat in November, and the race to succeed him will likely be competitive.
He will become the 15th Democrat to announce plans to leave the House at the end of this year.
Former Sen. Scott Brown, R-Mass., candidate for U.S. Senate in New Hampshire, holds his hand over his heart during the singing of the national anthem as he waits to take the stage for his town hall campaign rally with Sen. John McCain at the Pinkerton Academy in Derry, N.H., on Monday, Aug. 18, 2014.