So-called right-to-work laws—which are more accurately described as right-to-work-for-less laws, anti-union laws or poverty-producing laws—used to be a largely southern phenomenon in the United States. In the 20th century, cities in the northern U.S., from Philadelphia, Boston, New York City and Baltimore to Pittsburgh, Cleveland, Detroit and Milwaukee, were considered union towns, while many of the southern states were infamous for their hostility to organized labor. But in the 2010s, "right-to-work” laws have been making considerable progress in northern states. And far-right Republicans like Joe Wilson and Steve King in the House of Representatives have been calling for a right-to-work law to be enacted nationwide.

If a national "right-to-work" law were to be passed in both the House and the Senate (where it could face a Democratic filibuster), President Donald Trump—a supporter of anti-union legislation—would likely sign it. In that case, all 50 states would become "right-to-work" states whether they liked it or not. But even without a national law, anti-union legislation now prevails in Michigan, Wisconsin and other states that were once known for strong union protections.

Anti-union laws gained considerable ground in the southern states 70 years ago, when Congress passed the Labor Management Relations Act of 1947, a.k.a. the Taft-Hartley Act, and overrode a veto from President Harry Truman (who considered the law anti-union). The U.S.’ labor movement had grown considerably under President Franklin Delano Roosevelt’s New Deal in the 1930s and early 1940s—especially in the northern states and the Rust Belt—and Taft-Hartley, which was designed to slow down that growth, allowed individual states to pass right-to-work laws if they wanted them.

Under Taft-Hartley, employees in a so-called right-to-work state could not be compelled to join a union or pay union dues. A pattern began to emerge: Tennessee, Texas, Virginia, Georgia, Arkansas and North Carolina all became right-to-work-for-less states in 1947, while union representation was much stronger in Michigan, Pennsylvania, Wisconsin, New York, Illinois and other states that didn’t adopt anti-union laws. So if workers became employed in a unionized shop in Philadelphia or Detroit, for example, it was understood that they would be joining a union, paying union dues and enjoying all the benefits and advantages that came with unionization.

Although union leaders detested the Taft-Harley law and unsuccessfully fought for its repeal in the 1950s and '60s, the U.S. on the whole remained heavily unionized during those decades. Around 35% of U.S. workers—slightly more than one-third—were union members in 1954, but in 2012, that number was down to 11.3%, according to the Bureau of Labor Statistics (among private-sector workers, it was a mere 6.6%). Republicans, in 2012, were delighted to see unions having lost so much ground, and they were especially happy to see a great deal of anti-union activity in what had been traditionally pro-union parts of the country.

Although Barack Obama enjoyed strong union support when he was elected president in 2008 and reelected in 2012, many far-right Republicans were elected at the federal, local or state levels in 2010 and 2014. One of them was Rick Snyder, who was elected governor of Michigan in 2010 and signed an anti-union bill into law in that state in 2012. Indiana also became an anti-union state that year, and in 2015, Wisconsin became an anti-union state under Republican Gov. Scott Walker.

Kentucky and West Virginia—two of the more union-friendly southern states in the past—have also adopted anti-union laws in recent years, and Missouri, under Republican Gov. Eric Greitens, became a "right-to-work" state in February.

Nonetheless, some northern states have so far resisted anti-union laws, including Pennsylvania, New Jersey, New York, Illinois, Delaware, Ohio and the New England states. But if Republicans in Congress, with the help of Trump, succeed in passing a national right-to-work law, it will override any opposition on the part of Democratic governors like Tom Wolf in Pennsylvania or Andrew Cuomo in New York.

During a visit to Johnstown, PA in 2014, Wolf explained why he opposes making Pennsylvania an anti-union state.

“I don't really understand the logic behind it,” Wolf said. “In a democratic system, where the majority of workers vote to join a union, I’m not sure what gives a minority the right to say, ‘We’ll take advantage of the benefits of the union, but we’re not going to pay for the cost.’ It’s sort of like me, if I don’t vote for a particular governor, does that give me the right to say I’m not going to pay my taxes but I am going to use the roads and the bridges and things like that? I don’t think so. It seems to me it strikes at the heart of democratic fairness.”

The Pennsylvania AFL-CIO has sided with Wolf, saying that so-called right-to-work laws “weaken the best job security protections workers have: the union contract” and that it will oppose any bills that try to make Pennsylvania an anti-union state. But union-bashing Republicans dominate Pennsylvania’s state legislature, and at the federal level, far-right Sen. Pat Toomey—who narrowly defeated Democrat Katie McGinty in 2016 and was reelected to a second term—is an enthusiastic “right-to-work” supporter. While Philadelphia is controlled by Democrats and has long been a bastion of union activity, Central Pennsylvania (jokingly referred to as Pennsissippi or Pennsyltucky) is full of Republicans who would love to make Pennsylvania anti-union.

The fact that Trump, as filmmaker Michael Moore predicted, won three Rust Belt states (Pennsylvania, Michigan and Wisconsin) a Republican presidential candidate hadn’t won since the 1980s, underscores the inroads Republicans made in the northern U.S. during the Obama era. And many of them have been overtly hostile to unions, from Toomey to Rick Snyder to Scott Walker (who aggressively pushed for a law that in 2011, stripped most of Wisconsin’s public-sector workers of their collective bargaining rights).

Although Ohio has a Republican governor, John Kasich, and went for Trump in 2016, it has yet to become an anti-union state. But John Boyd, director of labor and legal affairs for the Ohio Chamber of Commerce, has been claiming that with Michigan, Indiana and Wisconsin having become right-to-work states, Ohio is now at a competitive disadvantage. And when in January, officials in the township of West Chester north of Cincinnati were calling for a local "right-to-work" law, Boyd noted, “Four out of the five states surrounding Ohio are now right-to-work.” The Ohio AFL-CIO, meanwhile, was vocal in its opposition to the West Chester proposal.

The AFL-CIO has also been attacking proposals to make New Hampshire New England’s first right-to-work state. In January, the GOP-controlled New Hampshire Senate passed an anti-union bill, which the AFL-CIO, the National Education Association and the Teamsters denounced as “an attack on all working families by special interests seeking to lower wages for everyone and undermine worker protections.” And New Hampshire Gov. Chris Sununu, a Republican and right-to-work-for-less advocate, would have signed it into law. But in February, the bill was defeated in the New Hampshire House of Representatives. According to the Bureau of Labor Statistics, unionization in New Hampshire has decreased from 11.1% in 2011 to 9.7% in 2015—and the bill, had it passed, would have likely brought that number down even more.

When the AFL-CIO and other critics of anti-union laws describe them as “right-to-work-for-less” laws, they aren’t merely being rhetorical; research demonstrates that these laws promote inferior working conditions. In 2011, a study by the Economic Policy Institute found that wages in anti-union states were “3.2% lower than those in non-RTW states” and that the rate of employer-sponsored health insurance was “2.6 percentage points lower in RTW states compared with non-RTW states….If workers in non-RTW states were to receive ESI at this lower rate, 2 million fewer workers nationally would be covered.” The study also found the rate of employer-sponsored pensions to be “4.8 percentage points lower in RTW states.”

Unions, in their 1940s/1950s/1960s heyday, were not only beneficial for union members, they were beneficial across the board because they set high standards in terms of pay, benefits and vacation time. When unionized plumbers, electricians, carpenters and constructions workers enjoyed positive working conditions, many white-collar professions also tended to have higher standards even if they weren’t typically unionized.

It is no coincidence that as union membership decreased in the U.S. in recent decades, overall conditions have worsened for both blue-collar and white-collar workers.According to Economic Policy Institute research, executives at large companies in the U.S. earned, on average, 296 times as much as their average workers in 2013 compared to only 20 times as much in 1965.

When Rep. Steve King introduced a bill calling for a national "right-to-work" law in 2015, it was merely symbolic; he knew that even if such a bill passed both houses of Congress and made it to the White House’s executive desk, President Obama would have vetoed it. But Republican proponents of a national law now have a more sympathetic figure in Trump, although such a bill would need some Democratic support in the Senate in order to survive a filibuster. Even without a national law, Republicans will no doubt continue to attack unions at the state level. Presently, 28 states have anti-union laws, and the more that number increases, the worse conditions will become for U.S. workers.