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. 

Updated at 1:50 a.m. ET: Mitt Romney won the presidential preference poll in the Washington state GOP caucuses Saturday, carrying forward his momentum from wins in Michigan and Arizona and setting the table for the crucial Super Tuesday gauntlet.

Romney and the other three remaining Republican presidential candidates waged a tougher-than-expected battle for Washington's votes, even though no delegates to the national convention were decided there.

Each candidate has spent time and money in recent weeks in hopes of picking up a victory -- and political momentum -- in Washington, as a table-setter to Super Tuesday, next week's slate of 10 caucuses and primaries across the country. 

Full Washington results can be found here.

After the results Saturday were revealed by the state party, Romney issued a statement congratulating his GOP rivals on their campaigns.

"We may differ from one another in background and experience," Romney said. "But we are united in our love of this country, and in our belief that with proper leadership America can do much better. The voters of Washington have sent a signal that they do not want a Washington insider in the White House."

In Seattle, Paul told supporters he was optimistic, NBC News reported.

"We know how to get delegates," he said, noting he is focused on an eventual delegate-building strategy.

The Super Tuesday contests in three days are expected to rehash the fight between Romney and Rick Santorum in Michigan, where Republicans handed the native Romney a narrow victory over Santorum. That battle is most focused in the critical state of Ohio although nine other states will be weighing in, including Georgia, Oklahoma and Massachusetts.

In years past, Washington’s contest was unimportant, taking place after the nomination was already by and large sewn up. In 2008, the Republican primary took place in late February after John McCain’s big night on Super Tuesday and after Romney had already dropped out of the race. This year’s attention from the press and the candidates is unusual, and underscores how difficult it's been for Republicans to draw their nominating process into an orderly conclusion.

Romney was in the state overnight Thursday and Friday morning. He raised $600,000 from supporters, and pleaded with supporters at a separate rally to show up on Saturday and participate in the caucuses.

"So I know most of you don’t know how to get to a caucus site. So if you go to Romney 'W-A' now -- you know what the 'W-A' stands for, RomneyWA.com -- it will tell you, if you put your address in, where the closest caucus site is," the former Massachusetts governor said. "Then you can show up and it won’t take a long time, it will just make a big difference. So please make sure and go to the caucus site. Get your friends to do the same thing."

Romney's hoping to build on momentum from this past Tuesday, when he easily won Arizona's primary and edged Santorum in his native Michigan.

Santorum was in Washington as recently as Thursday, and he decried the GOP's "good 'ol boys" who wish to see Romney become the nominee.

"The best chance for us to win is to not to go along with the good ol' boys who always want to nominate a moderate. The best chance for us to win is to create clear, sharp contrasts," Santorum said, continuing with a line of attack that almost scored him an upset win over Romney in Michigan earlier this week.

Santorum -- as well as Gingrich -- each swung through the state in mid-February around the time the state's Democratic governor signed into law new legislation legalizing same-sex marriage in the state.

“This is the first time in our history that all the candidates have come out before the caucuses,” said Kirby Wilbur, the chairman of the Washington GOP. “For a political party, it’s exciting when the candidates pay attention to you.”

Paul, the Texas representative, also spent Friday in Washington. His campaign has focused more intently on caucuses rather than primaries because caucuses tend to favor the type of enthusiastic supporter Paul enjoys. But he has not been able to win outright any of the caucuses to date.

Unlike some of the other major primaries to have taken place, though, the candidates have spent a minimal amount of money on advertising in the state. Paul's campaign has spent $48,000, and Santorum has spent $25,000.

Like most other caucuses to have taken place, no actual delegates will be formally awarded on Saturday.

Two sets of results were coming out of Washington on Saturday night. First was the results from a straw poll of caucus attendees. The straw poll is conducted at sign-in, and then caucusgoers are encouraged to remain at precincts to elect delegates to the state convention in June. That convention will actually determine the allotment of Washington's 43 delegates.

Wilbur said the late selection process could keep the state in the national spotlight if the Republican nomination fight becomes a protracted hunt for delegates.

“If we don’t have a clear winner in another month or so, I’ll think they’ll come back,” he said. “We’ve got 40 delegates at stake at our state convention in May and they’ll need those 40 delegates if it’s still a two- or three-man race going down the stretch.”

The Washington contest serves largely as a precursor, though, to Super Tuesday. In a nomination fight that may turn into a protracted battle for delegates, individual contests become more important to each candidate.

Regardless, the state party is happy to have the candidates and media focus on the state like never before.

“We’ve never had this kind of attention,” said Wilbur. “We were always the ugly sister never invited to the dance and now we’re the princess.”

NBC News contributed to this report.