Senate Democrats introduced legislation Wednesday to repeal all state right-to-work laws, arguing that the laws, which prevent workers from being forced to join or financially support a labor union as a condition of employment, are wrong because they make it harder to form unions.

"So-called right-to-work laws give corporations the ability to trample workers' rights and dismantle unions. I refuse to let that happen. At a time when Americans are working harder and earning less for the time they put in, we should be making it easier for workers to raise their voices and bargain for better wages and safer working conditions. Right-to-work is really right to work for less," said Sen. Sherrod Brown, D-Ohio, a co-sponsor of the legislation. Sen. Elizabeth Warren, D-Mass., is the lead author.

The legislation is two sentences long: "This act may be cited as the 'Protecting Workers and Improving Labor Standards Act'. Subsection (b) of section 14 of the National Labor Relations Act (29 U.S.C. 164) is repealed."

Organized labor is a major source of campaign funding for the Democratic Party, giving more than $59 million in the 2016 election cycle alone, according to the Center for Responsive Politics. Conservative groups put the amount that unions gave to Democrats, liberal activist groups and political action committees between 2012 and 2016 at $765 million.

State right-to-work laws specifically prohibit union-management contracts that require all workers join the union or pay it a regular fee. The provisions, dubbed "security clauses" by unions, are common in non-right-to-work states. Unions argue they are owed the money to pay for collective bargaining expenses that benefit workers. Business groups and Republicans back right-to-work laws, arguing they give states an edge in attracting business and that joining a union should be up to individual workers, not employers and union leaders acting together.

A total of 27 states have the laws. Five states have adopted them since 2012, including Michigan and Wisconsin, both of which border Canada. Another state, Missouri, passed one but it is on hold pending the outcome of a union-backed voter referendum. Several of the laws date to the 1940s when they were first allowed by the 1947 Taft-Hartley amendments to the National Labor Relations Act. Prohibiting them would severely disrupt business practices in those states.

The funds provided through right-to-work laws are a major source of union revenue. Until recently, unions assumed that all of the states open to the laws had already adopted them, but the recent passage of versions in states with strong pro-labor histories such as Wisconsin, Indiana, and Michigan have left union leaders shaken.

"You never say right-to-work in the union movement because it is a great example of naming something. Pretty often you cannot even explain right-to-work to union members without them thinking it sounds like a pretty good idea," Ben Johnson, former head of United Professions AFT Vermont, the union's state umbrella organization, told the Washington Examiner last month. Leaders struggled to come up with a euphemism that would make it sound bad. The most commonly used one is "right to work for less," which tries to present the laws as weakening unions and therefore workers' bargaining strength.

Unions have attempted to attack the laws from several novel angles. Wisconsin unions challenged their state's law as an unconstitutional "taking" of their property, an argument recently rejected in federal and state court. The Canadian government, prompted by its unions, has attempted to use the North American Free Trade Agreement renegotiations to get the U.S. to ban the laws, but the Trump administration has reportedly refused.