WASHINGTON — The AFL-CIO launched a $40 million voter-drive yesterday, targeting 21 states and hoping increased turnout among union members swings competitive races in Ohio and Pennsylvania.

The financial commitment amounted to the most expensive by the union for the midterm elections. The focus is 21 governors races, 15 Senate races, and at least 50 House races.

The AFL-CIO said its effort could reach 12.4 million new voters — union members, their households, and families — in those top-tier states. The vast majority of the candidates who would benefit are Democrats in union-heavy states, especially the Midwest.

By its estimates, the AFL-CIO is counting on a 5% increase in turnout. If successful, the union said, it would add 310,000 union votes to Democrat Ted Strickland’s race for Ohio governor. Pennsylvania union voters could boost Democrat Bob Casey’s bid to unseat Senator Santorum by 155,000 votes.

“It’s a sustained effort of communicating with members. We do a lot of research where members are and what they think about and what moves them,” the AFL-CIO’s political director, Karen Ackerman, said. “It really is a very sustained effort — months and months and months.”

The $40 million does not include the roughly $1.5 million in political action committee funds that the AFL-CIO contributes each election. It also excludes direct contributions to individual candidates from members.

“We don’t expect all union members will vote for the union-endorsed candidate,” Ms. Ackerman said.

But union critics said such activism alienates many would-be union members.

“Rather than working to expand their political clout, union officials should instead clean up the corruption, shun the political activism, and turn their energy to improving the product they’re attempting to sell to America’s hardworking men and women,” Justin Hakes of the National Right to Work Legal Defense Foundation said in a statement.

The 2006 campaign also is the first since six unions left, fracturing organized labor’s political efforts that largely have benefited Democrats.

Change to Win, which represents six unions and 7 million workers, was formed in 2005. But it is focused more on organizing and has joined forces with the AFL-CIO political effort.

At a news conference, Change to Win leaders addressed the split by highlighting successes in organizing new workers.

The AFL-CIO’s president, John Sweeney, told reporters later that the leaders of the two organizations share common goals. He said the majority — or at least four — of the Change to Win constituent groups were interested in participating in the long-standing operation.