Larry Enman, a Democrat from Errol, has beaten Republican incumbent Duffy Daugherty in Coos District 1 by 20 votes, according to a final tally by the Associated Press.
In a telephone interview Daugherty said he did not intend to seek a recount, describing the statewide election as a sweep.
"The state is going to hell in a hand basket and I'm not going to fight it," he said.
With all 10 precincts counted Enman had 1,158 votes compared to 1,138 for Daugherty.
Official figures from the Secretary of State are not yet available.
Incumbent Republican Larry Rappaport, of Colebrook, was re-elected to the second seat with 1,540 votes.
Rappaport is a well-known opponent of Northern Pass who introduced a bill that became law and has the effect of making it difficult for project to use eminent domain.