Elaine Thompson / AP

Democrat Jay Inslee

Democrat Jay Inslee has won the Washington state governor’s race, NBC News projected Friday night.

Republican Rob McKenna called Inslee shortly before 6 p.m. Pacific Time to concede the race and congratulate the governor-elect on winning, Randy Pepple, McKenna’s campaign manager told reporters, the Seattle Times reported.

With the Washington race conceded, Democrats won seven out of 11 governor races this year.

Inslee thanked McKenna, Washington’s attorney general, for what he described as a gracious conversation, The Associated Press reported. Inslee was a U.S. representative but resigned last March to focus on running for the governor’s seat.

The decision brings to end one of the most-watched, most-expensive gubernatorial races in the country. The two candidates and outside political groups raised and spent some $40 million in the race.

Inslee's campaign was built largely around his plans to spur job growth by investing in clean energy and other specific sectors.

Both candidates vowed to not raise taxes, but in January lawmakers will begin negotiations over how to deal with a budget shortfall and the need for more education funding.

Inslee has already started the process of forming a team that will help him transition to office, AP reported.

Inslee had steadily held a 51 percent advantage in the race as ballots were counted this week.

Republicans last won a Washington governor's race in 1980, when John Spellman was elected. 

Elaine Thompson / AP

Rep. Jay Inslee, D-Wash. wants to focus full time on running for governor of Washington state this fall.

Updated at 4:44 p.m. ET: SEATTLE -- Rep. Jay Inslee is resigning from Congress to focus full time on running for governor of Washington state this fall.

Inslee, a Democrat in his eighth term representing the Seattle-area 1st District, announced his decision Saturday ;at a news conference in Seattle.

Washington's Democratic governor, Christine Gregoire, is retiring at the end of her term, and Inslee wants to suceed her. State Attorney General Rob McKenna is the leading Republican candidate for governor.

Inslee is among 22 Democratic members of the House who are not seeking re-election, along with 16 Republicans.

If Inslee had resigned by March 6, Gregoire would have had to order a special election to fill his congressional seat, setting off a scramble among the half-dozen candidates in the 1st District race, according to The Seattle Times. But if he steps down March 7 or later, his seat would remain vacant until after the November elections, the newspaper said.

His resignation is effective March 20.

President Barack Obama praised Inslee's political accomplishments.

"Through the course of more than 20 years working on behalf of Washington state, including more than a decade in Congress, Jay Inslee has never forgotten where he came from," Obama said in a statement issued by the White House. "A son of the Pacific Northwest, Jay has been a champion of our natural resources while pushing for new sources of clean energy. Jay has supported new frontiers in technology, and worked to increase fairness in our nation's health care system. While Jay's voice in Congress will be missed, I know he will continue his dedicated service to the people of Washington state."

The Associated Press contributed to this story.