PORTLAND (AP) — A ballot measure that would undercut the economic power of the state’s public employees unions continued to hold a slim lead Wednesday but the outcome remained too close to call.

With 75 percent of the vote counted, 50.5 percent of voters supported Measure 64 and 49.5 percent opposed it. A batch of ballots from Multnomah County had yet to be counted.

“It’s razor thin,” said political activist Bill Sizemore, who sponsored the measure. “We don’t have a good feel for how Multnomah County could go.”

But Scott Moore of the Defend Oregon Coalition, a union-based organization that campaigned against Measure 64 and four others put on the ballots by Sizemore, said he expected the final results would show voters rejected the measure.

If passed, the measure would bar public employee unions from using money from payroll deductions on political campaigns. Sizemore, who said the measure would keep the government neutral on elections, has tried and failed to pass similar measures in the past.

His opponents argue Measure 64 unfairly targets government employees and has such broad language that it would not only limit unions contributions to political campaigns but to charities, too.

“It would severely limit working Oregonians from participating in the political process,” Moore said, “and it would leave the door wide open for corporations and out-of-state millionaires.”

Sizemore’s other measures proposed changes in the state school system and attempted to loosen rules on tax deductions and building permits. All were rejected.

One reason the vote tally on Measure 64 remains so close, Moore said, is because it was the only one of Sizemore’s measures that he and his supporters spent a significant amount of money on.

Sizemore’s work was financed by Loren Parks, the owner of a medical equipment company in Aloha who moved to Nevada in 2002, and the Republican-leaning group Freedom Works. Sizemore said that of the five measures he authored, Measure 64 was his top priority.

Public employee unions spent more than $15 million on ballot measure campaigns, primarily fighting Sizemore’s measures.

“It has become very clear that Bill Sizemore’s attempt was to divide labor unions and organizations in the state by putting a number of measures on ballots and divide their attention,” Moore said.

If Measure 64 is approved by voters, Moore said Defend Oregon will consider taking legal action, because it's possible the measure would deny the union members from practicing free speech rights. Sizemore disagreed.

“I think we’ll look very seriously at whether the measure is legally sound,” Moore said. “Similar measures passed in other states have been thrown out by federal appeals courts.”