Updated 9:11 a.m.

PORTLAND (AP) – Democratic challenger Jeff Merkley has unseated two-term incumbent Republican Gordon Smith in a hard-fought U.S. Senate race.

It was the most expensive race in Oregon history, with spending estimated at more than $40 million. A flood of votes Oregonians delivered on election day kept election workers tallying ballots for two days.

The victory gives Democrats at least 57 votes in the U.S. Senate with the outcome of three other races yet to be determined.

Merkley planned an appearance Thursday morning to claim victory, and Smith planned a press conference Thursday afternoon.