Inslee outgained McKenna in Tuesday's tally of ballots by a margin of 46.8 percent to 42.9 percent.
Shoreline businessman Rob Hill, a Democrat, was a surprising third followed by conservative Republican candidate Shahram Hadian of Everett, who garnered 2.4 percent, according to results compiled by the Secretary of State.
Ballot counting continues today with updated results to be released this afternoon.
Inslee, who resigned from Congress in March to focus full-time on the race, called the results an "important milestone."
"My wife, Trudi, and I look forward to campaigning across the state in the coming weeks, and talking with middle-class families about Washington's economic future," he said in a statement. "After all, this election is all about the future. And if given the opportunity, my term as governor will be about building a better future for the people of Washington.
McKenna, in his second term as the state's attorney general, is trying to become Washington's first Republican governor since John Spellman three decades ago.
He downplayed the importance of the primary, insisting in the days leading up to the vote that he'd finish behind Inslee in the balloting.
"We have been at this for over a year. Primaries pit people in the same party against each other, but when they're over, it's time for folks to join together to work for a better state," he said in a statement.
Most of McKenna's statement focused on his differences with Inslee.
"The choice that faces us is in this election, is do we keep electing the same people who have been digging a deeper hole, or do we put a new team on the field to make tough decisions?" he said.
McKenna, 49, of Bellevue, was elected as Washington's attorney general in 2004, and targeted meth use, gangs, sex offenders, identity theft and Internet predators
Inslee, 61, of Bainbridge Island, served 15 years in Congress where he's made his mark as a voice for alternative energy development and environmental protection.
In the campaign thus far, they've split on some major issues such as charter schools, which McKenna supports and Inslee opposes.
Gay marriage is another. Inslee supports the state law allowing gay and lesbian couples to marry while McKenna wants to repeal it.
On the other hand, both are pledging to pour billions of dollars into public schools and colleges without raising taxes. And they each say their primary goal is reviving the economy.
McKenna does lead in fundraising though both have hauled in more than $7 million.
The other candidates in the race are Sultan computer programmer L. Dale Sorgen, holistic health proponent Christian Joubert of Edmonds, Black Diamond airplane parts painter Max Sampson, Marysville airplane inspector James White and retired Bucoda resident Javier O. Lopez.
Jerry Cornfield: 360-352-8623; email@example.com
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