Missouri union activists turned in more than 310,000 signatures Friday to ensure a fall ballot referendum asking voters whether they wanted to keep the state's right-to-work law. The outcome of the referendum is likely to hinge on the way it is written on the ballot — and the union activists already have won a key battle on that front.

Right-to-work laws prohibit workers from being forced to join or otherwise support a union as a condition of employment. The issue may seem technical but it can have a huge impact on how powerful unions are in a state. Unions hate the laws because they are associated with membership losses and depleted treasuries. Business groups and Republicans back the laws, arguing that the choice of supporting a union should be up to individual workers. Missouri adopted the law in February, becoming one of six states to have adopted a version since 2012. The law was to have taken effect Aug. 28 but is on hold pending the outcome of the referendum.

Last month, the Missouri AFL-CIO won a key battle when an appeals court ruled in favor of the ballot language it wanted for the referendum. The language asks whether voters "want to adopt" the right-to-work legislation. A lower court had previously thrown out the language, arguing it would confuse voters since the state had already adopted the law, and voters were actually being asked whether they wanted to repeal that law. The appeals court overruled the lower court, saying that the ballot language needn't be "grammatically competent."

That could be key in the outcome, says Mark Mix, president of the National Right To Work, which is pushing for the law. "Obviously, the unions want to confuse people. Confusion usually militates in favor of a 'no' vote," he said. A referendum that would ask voters whether they wanted to throw out an existing law would have less chance for success, he argued.

Mix points to the case of Virginia, where a Republican-backed ballot initiative to make right-to-work part of the state Constitution was defeated, 53-47 percent last year. He said the language, which didn't make clear that Virginia was already a right-to-work state and that voters were merely being asked to further codify that, contributed to its defeat. "And that was language that was written by our so-called allies," Mix said.

Ballot fights regarding right-to-work face the additional hurdle that the law's concept isn't widely understood by the public, less than 11 percent of whom are union members, according to the Labor Department. Most states that adopted the laws did so in the 1940s and 1950s, and it rarely came up in the decades since then. Until recent years, it was believed that that all of the states open to right-to-work had already adopted it. The issue's revival has had both sides scrambling to educate voters. Unions in particular have had a hard time coming up with rhetoric to address the issue.

"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," said Ben Johnson, former head of United Professions AFT Vermont, a state teachers' union federation. 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. But even that conveys the basic idea of right to work.

At a rally on the steps of the Missouri statehouse Friday to turn in the signatures for the ballot referendum, speakers mostly avoided the question of what the law they were opposing actually did. Dennis Palmer, a union-friendly owner of an electrical contracting business, was a rare voice who addressed the issue head-on. "An owner of a company should have the freedom to require union membership as a condition of employment to ensure our highly skilled workers," he said. A union representative could not be reached for comment.

Missouri Republicans have argued that unions have tried to capitalize on any confusion in their effort to throw out the laws. "Union bosses and Big Labor groups are being dishonest with Missourians about right-to-work, and as a result, we are seeing thousands of people rescind their signature from these anti-right-to-work petitions," said Missouri Republican Party Chairman Todd Graves Friday. The party cited a claim by the Liberty Alliance, a political action committee backing the right-to-work law. The PAC could not be reached for comment.