Incumbent Sen. Ed Markey’s advantages as the sitting senator, combined with endorsements from Sen. Elizabeth Warren, Sen. Bernie Sanders, and Rep. Ayanna Pressley, have anchored trader consensus around an 84% implied probability of his Democratic primary win on September 1. Recent August debates with Rep. Seth Moulton highlighted differences on affordability, immigration enforcement, and age limits for Congress, yet polls from Emerson College and the University of New Hampshire show Markey maintaining a lead despite tightening margins and rising undecided voters. Moulton’s endorsements, including from Gov.-elect Mikie Sherrill, and criticism of Markey’s reelection bid have supported his 16.5% odds but have not overcome the incumbent’s structural edge in a short campaign window. Minor candidates like Pressley and Alexander Rikleen register negligible probabilities.