Just about every congressional session, Republicans unveil what's known as a "right to work" bill. Under the guise of liberating workers, these measures make it harder for unions to collect dues, limiting their power on the job and in the political arena. Championed by business lobbyists and loathed by organized labor, the federal version, which covers the private sector, is typically seen as pie-in-the-sky legislation not worth getting too riled up about on either side.

But the latest iteration — introduced by Congressmen Joe Wilson (R-SC) and Steve King (R-IA) earlier this month — is triggering an emphatically different reaction within union ranks.

"I can't remember a time when it was this serious of an attack," labor lobbyist Ken Zinn told the Voice. Zinn has worked in Washington for over three decades and is currently political director for National Nurses United, a labor union that represents approximately 185,000 registered nurses across the country. "It's certainly something we and everyone else should be extremely worried about."

A national right-to-work law — versions of which are already on the books in 28 different states — would eliminate "union security" clauses, a standard part of labor contracts, that require workers to pay fees to labor organizations that bargain on their behalf. When in place, they solidify a key source of revenue for unions. Right-to-work strangles that revenue.

The measures ultimately affect the entire workforce, union and non-union alike: Workers in right-to-work states earn 3.1 percent less than those in other states, according to the left-leaning Economic Policy Institute. The workplace fatality rate also tends to be higher in states with such laws.

The current Republican-dominated government has created arguably the most favorable landscape for national passage since the measures first cropped up in the South in the World War II era. Since their introduction, the laws have had a sordid history.

The first right-to-work push kicked off in Texas in 1941, against the backdrop of a national wave of union organizing wins and New Deal reforms that brought the labor movement to the doorstep of the largely union-free South and Southwest. Anxious about the rapidly changing tide, a group of conservative small-business owners, under the banner of the Christian American Association, began to lobby against mandatory union dues. Heading the group was Vance Muse, a former oil industry lobbyist later described by his own grandson as a "white supremacist, an anti-Semite, and a Communist-baiter" who opposed women's suffrage and child labor laws. He warned the local press of a "red radical scheme to organize Negro maids, cooks, and nurses in order to have a Communist informer in every Southern home."

By the end of the decade, Texas and eleven other states had passed right-to-work laws, and more mainstream trade associations had adopted the cause. More recently, as the GOP has seized control of state governments and labor's clout has waned, a flurry of states have passed similar laws, including Kentucky and Missouri this year. Labor has also dodged some bullets: The U.S. Supreme Court seemed poised to institute public-sector right-to-work before Justice Antonin Scalia's death last year. New Hampshire legislators also narrowly voted down right-to-work last Thursday, bucking the state's new Republican governor.

Contemporary supporters of right-to-work, like the U.S. Chamber of Commerce, the Koch-funded Americans for Prosperity, and a constellation of conservative think tanks, see the issue as one of individual liberty. The measures lead to "increased worker freedom," said Representative Wilson, perhaps best known for disrupting President Obama's address to a joint session of Congress in 2009 by shouting, "You lie!" "Nothing in this legislation prevents people from joining unions or prevents unions from operating."

Right-to-work measures ultimately affect the entire workforce, union and non-union alike

Opponents counter that the fees exist to combat the so-called free-rider problem: Under U.S. labor law, unions are obligated to represent every member covered by the contracts they negotiate. Mandatory dues ensure that everyone pays for the benefits they receive. For union leaders, the objective of eliminating this requirement is clear: Right-to-work is about starving the labor movement of resources, diminishing its ability to defend its membership and progressive causes at large.

"This law is an attempt to disable the only movement of working people in America so that corporations can come in and exploit them," said Larry Hanley, president of the Amalgamated Transit Union (ATU), which represents 190,000 workers across the U.S. and Canada. "It's hard to explain that in three words like 'right to work,' but that's really what it is. It is a coup d'état against working people."

House Republicans can probably pass Wilson and King's bill easily. Matters are more complicated in the Senate, where Democrats enjoy the ability to filibuster, although Republicans have the ability to change Senate rules and begin adopting laws by a simple majority.

The wild card at the top is President Trump. Despite portraying himself as an ally of American workers and campaigning, in part, on classic union themes like opposition to outsourcing and free trade agreements, he has also said he supports national right-to-work.

"How serious they want to push this is the question, and I just don't think we know the answer to that," said Zinn. "Everything we've seen so far with the president of the United States is that he's a very unpredictable person," but nevertheless, "we have to treat it like they're serious."

Trump has also made overtures to the most conservative wing of the labor movement, the building and construction trades. Last month, he invited its leaders into the White House, wooing them with talk of infrastructure development and earning their praise for an executive order approving the Keystone XL pipeline. National right-to-work risks disrupting this courtship and the prospects of a future alliance. (Representatives from the Laborers' International Union of North America and North America's Building Trades Unions, an umbrella group, did not respond to requests for comment.)

In spite of the circumstances, Hanley, the ATU president, remains optimistic. "I take a longer view," he said. "This could be the administration that permanently turns America to the left, because most of what we see is so inherently anti-American."