Walker's facing a fresh union offensive. (AP Photo/Jeffrey Phelps, File)

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The nation’s largest public sector union is mounting an intense effort to eject Wisconsin Gov. Scott Walker from office this fall, determined to oust the Republican who punctured the power of organized labor in the state.

“We have a score to settle with Scott Walker,” Lee Saunders, president of the American Federation of State, County and Municipal Employees, said in his first interview about the union's midterm strategy.

“He took collective bargaining away from us,” Saunders added, noting that the union was first started in the 1930s by state employees in Madison. “He stole our voices, in a state where we were born.”

A spokeswoman for Walker, who is in a tough reelection fight, did not respond to requests for comment.

Walker is in a tough reelection fight against Democratic challenger Mary Burke.

Alleigh Marre, a spokeswoman for the governor, said in a statement that “the big government union bosses are bitter about Governor Walker's reforms which have saved taxpayers $3 billion to date, and they're going to stop at nothing to undo the recall by bankrolling Mary Burke's campaign.”

“When the union bosses say they 'have a score to settle with Scott Walker,' they really mean Wisconsin taxpayers because that's who Governor Walker is protecting with his reforms,” Marre added.

Saunders said the 1.6-million-member union is also devoting sizable resources to trying to prevent a “Wisconsin moment” in other states by backing Democratic gubernatorial candidates in Connecticut, Florida, Michigan and Illinois.

Saunders said that the union would have 40,000 staff and volunteers deployed in key states in the run-up to November’s election, focused on both gubernatorial and U.S. Senate campaigns. The strategy, he said, is "basic one-on-one organizing" -- door-knocking, phone banking and visiting work sites. Because of the Supreme Court's Citizens United decision, labor unions have been able to expand their ground operations and can now target all voters, not just their members.

AFSCME can muster substantial financial resources, as well. During the 2010 midterms, union officials said they poured roughly $90 million into local, state and federal campaign efforts.

Saunders declined to specify how much AFSCME would pump into politics this year, saying only: “We play hard.”

The union’s top target is Walker, whose 2011 legislation curbing the collective bargaining rights of public employees set off a political storm. The law, which prevents the automatic deduction of union dues from worker paychecks, has cut deeply into the membership of AFSCME and other unions in Wisconsin.

“We’ve lost 70% of our membership in the state,” said Saunders, adding that the union is down to about 25,000 members there. “But let me tell you something: the members that remain are some of the most committed and dedicated members that we have all across this country.”

Walker survived a contentious recall attempt backed by AFSCME and other unions in 2012. But labor officials said that they believe they have a better shot defeating the governor in a normal election year. A Marquette Law School poll taken in late August showed Walker in essentially a dead heat with Burke.

“I believe for the most part that people don’t like recalls,” Saunders said. “I think people say he got voted into office…you’ve got to give him the opportunity to continue to serve. Some of our members felt that way. But this is an election in which we have an opportunity to change the course.”

Tom Hamburger contributed to this report.