In Michigan, Gov. Rick Snyder signed legislation last week prohibiting unions from requiring workers to pay dues or representation fees, even if they are covered by union contracts.
It was another jarring blow for unions in Michigan, a cradle of the modern American labor movement. Unions already had spent $22 million this year in the state on a failed effort to enshrine collective bargaining rights in the Michigan Constitution.
Unions are gearing up for another expensive fight in the state. They hope to collect enough signatures for a "statutory initiative" that would let the state's voters cast a ballot for or against "right-to-work," a measure that would essentially override the substance of the new law.
But the symbolism of the law's enactment in pro-labor Michigan has given conservatives high hopes they can succeed elsewhere. Mark Mix, president of the National Right to Work Committee, said his group now is eyeing Alaska, Missouri, Montana and Pennsylvania.
"We think there's a chance just about everywhere now," Mix said.
Democratic governors in Missouri and Montana would likely block such measures. In Pennsylvania, Republican Gov. Tom Corbett recently said his state lacks the political will to change the labor laws, despite Corbett's support and GOP control of the Legislature.
So far, the costly battle has produced mixed results for organized labor.
Unions spent $24 million to overturn an anti-union measure in Ohio in November 2011, only to lose their effort to recall Wisconsin Gov. Scott Walker the following June. Unions spent more than $20 million in Wisconsin to defeat the Republican in a special election after he signed legislation the year before stripping most public employees of much of their collective bargaining power.
This year, an effort to defeat a California ballot measure that would curb dues-collection for political spending cost unions more than they spent in Michigan, Ohio and Wisconsin combined.
"Clearly, this is a strategy by the ultraconservatives to make us spend our resources, but we have no choice," said Lee Saunders, president of the American Federation of State, County and Municipal Employees, the nation's largest public employees union.
The mixed bag belies labor's successful fall campaign this year.
Across the country, unions helped elect Democratic governors, build labor-friendly majorities in state legislatures and defeat ballot initiatives. They also played a key role in helping President Barack Obama win swing states including Ohio, Nevada and Wisconsin, according to exit polls.
But amid the costly battles over dozens of measures across the country, overall union membership has shrunk to just 11.8 percent of the workforce. It could hit another historic low this year after public sector unions lost thousands of members in Wisconsin and in other states that have turned to layoffs due to budget shortfalls.
Labor leaders point to Snyder and Walker as their prime targets in the 2014 elections. However, Walker is seen as having the upper hand in light of his win last summer in the highly publicized recall election.
Walker raised more than $30 million to beat Democrat Tom Barrett in the June recall by almost 7 percentage points, a wider margin than their first face-off in the November 2010 election.
"Gov. Walker is a national figure now and has already faced down a direct challenge from labor, a benefit he did not have in 2010," said Walker adviser Dan Blum.
The AFL-CIO's Podhorzer said unions also plan to target Ohio Gov. John Kasich, who was seen as weakened when his enactment of a measure limiting public employee bargaining rights was overturned by referendum. Kasich's approval in surveys of Ohioans has improved somewhat, although it remains below 50 percent.
Hungry for a win, unions also are circling Corbett in Pennsylvania and Florida Gov. Rick Scott. Though the states are expensive for advertising, the Republican governors are seen as vulnerable, with approval ratings below 40 percent in November.
While defeating Corbett, Kasich, Snyder or Walker would strike a blow for more traditionally pro-labor manufacturing states, the chance to defeat Scott is seen as a potential bright spot for labor's future.
"Florida is different. It's one place where unions are trying to expand," said Florida Democratic strategist Steve Schale.
Florida is a weak labor state, but one where the heavy presence of service-sector jobs gives large and newer unions such as Service Employees International Union an opportunity to grow.
Former Gov. Charlie Crist, who left the Republican party and has changed his affiliation to Democrat, is eyeing a run for governor in 2014. Crist was seen as a defender of public-sector unions.
Conservative groups deny claims that the push for right-to-work laws and other anti-union measures is part of a concerted GOP effort to weaken unions because they are a pillar of Democratic candidates and causes.
"It means that Michigan is going to be more prosperous and workers there are going to have more freedom and choice when it comes to a union," said Tim Phillips, president of Americans for Prosperity, which has funded anti-union measures in Michigan and around the country.
But Phillips said the decrease in union membership "does impair their ability to just bully people politically, which they've done for a long time."