Charter-school supporters claimed victory Saturday, but opponents refused to concede in the face of a vote tally that remains too close to call.

Charter-school supporters claimed victory Saturday, but opponents refused to concede in the face of a vote tally that remains too close to call.

As of 7 p.m., Initiative 1240 was leading 50.8 to 49.2 percent, the same margin as Friday. The measure continued to trail in King County, with 51.5 percent of voters against, but maintained its lead in the rest of the state. About 400,000 ballots are left to count statewide, with 130,000 in King County. The measure is leading by 43,860 votes statewide.

“We’re going to wait until every vote is counted,” said Marianne Bichsel, spokeswoman for the anti-charter group People for Our Public Schools.

But initiative supporters said they’re confident they’ve won.

“We’ve maintained a lead the whole time,” said Jana Carlisle, executive director of Partnership for Learning, a founding member of the coalition that backed the measure. Reversing the trend would require an improbable turn of events, she said.

The initiative would authorize the creation of 40 publicly funded, privately run charter schools.

Three previous attempts to approve the creation of charter schools were defeated by state voters.

In this year’s election, supporters outspent opponents by a 10-1 ratio, raising more than $10 million from donors that included Microsoft co-founder Bill Gates.

“We were so outspent, it’s incredible the race is this close,” Bichsel said.