BOSTON (AP) — Steve Kerrigan, the 2014 Democratic nominee for lieutenant governor, is dropping out of a crowded field of candidates hoping to succeed retiring Democratic Rep. Niki Tsongas.

Kerrigan, whose mother recently died, said in a message to supporters Monday that he has decided to end his campaign for Congress. He said he has no plans to make an endorsement before the Democratic primary.

Kerrigan said the death of his mother "has been an incredibly difficult time for my father, brother, sister and our whole family."

The race for the 3rd Congressional District is one of the most closely watched contests this year in Massachusetts.

About a dozen Democratic candidates and a handful of Republicans are vying for the seat.