WASHINGTON -- Sen. George V. Voinovich said yesterday that he will oppose a bill championed by organized labor that would make it easier to expand membership

In a letter that his staff released to the media, the Ohio Republican wrote that he will vote against the measure because it would allow unions to organize by collecting signatures on cards instead of voting by secret ballot.

"The secret ballot is a cornerstone of American democracy," Voinovich wrote. "I believe this process protects the individual right to make a private choice."

Voinovich released his letter on the same day that Sen. Arlen Specter, R-Pa., announced that he will oppose the bill, which is labor's top legislative priority. Organized labor had counted on Specter to provide the 60th vote necessary to end an expected Republican filibuster when the bill comes to the Senate floor this summer.

Although Voinovich had never been considered a likely supporter of the bill, his aides said the letter firmly ends any speculation that labor could win his vote.

Joe Rugola, president of the Ohio AFL-CIO, said he is disappointed in Voinovich's decision but "not a bit surprised. In our evaluation of potential voters around the country ... I always had Voinovich listed as a certain 'no.'  "

But Rugola, who was in Washington yesterday to meet with labor leaders, said Specter's decision "presents a huge problem for organized labor."

President Barack Obama has pressed for congressional passage of the bill, which the Democratic-controlled House probably will approve. Proponents have said the measure is badly needed to reverse a trend of declining union membership.

But major U.S. companies have opposed the measure, saying the card check could lead to union leaders intimidating workers into organizing a union.

jtorry@dispatch.com