Third District race remains too close to call

Lori Trahan speaks after a close win in the Democratic Primary.
Congressional candidate Lori Trahan addressed supporters in Lowell. She claimed victory in the Third District race, but rival Dan Koh refused to concede. –Josh Reynolds for The Boston Globe

In a race that long ago ditched clarity, the Third Congressional District’s Democratic primary dragged into early Wednesday morning, with two candidates knotted in a too-close-to-call race in the most crowded congressional field in a generation.

The campaign of Lori Trahan, a former Capitol Hill aide, claimed victory with a razor-thin margin over Dan Koh, the former chief of staff to Mayor Martin J. Walsh.

“I stand before you humbled, honored and leading as your Democratic nominee for Congress,’’ Trahan, a Lowell native now living in Westford, told a cheering crowd at the UMass Lowell Inn and Conference Center.