Democratic challenger Seth Moulton defeated 17-year-incumbent U.S. Rep. John Tierney Tuesday night in the most closely watched congressional primary in the state's 6th Congressional District.
Tierney conceded the race just before 9:30 p.m., with just 26 percent of the vote in.
Tierney had said he was confident of victory but his campaign recently launched an ad targeting Seth Moulton, a businessman and Iraq War veteran hoping to unseat him.
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