ANNAPOLIS, MD (AP) – Maryland U.S. Sen. Ben Cardin will retire at the end of his third term. His announcement triggers what is likely to be a highly competitive primary to replace him. The 79-year-old Cardin is the third Democrat senator to decide not to seek reelection next year. Potential candidates for Cardin’s seat include Democrat Reps. David Trone and Jamie Raskin. Democrats outnumber Republicans 2-1 in Maryland, which has not elected a Republican to the U.S. Senate since 1980.