A minimum-wage protest in Washington state. (Ted S. Warren/AP)

In November, minimum-wage advocates scored one of their biggest victories in decades as voters resoundingly approved raising the minimum wage in four out of four states.

But in three of those states, the battle isn't over. Minimum-wage advocates are scrambling to defend their nascent victories in courts and in state legislatures across the country. In some cases, they could be victims of their own success: The very ballot initiative tools they used to raise the minimum wage — especially handy in states controlled by Republicans opposed to minimum-wage increases — could be blunted or their results reversed.

In Washington and Arizona, various food and business groups are challenging the constitutionality of the minimum-wage increases that voters approved by double digits. In Arizona, the legislature is moving to give itself power to repeal any approved ballot measure. In Maine, where voters approved the strongest minimum-wage increase in state history, the restaurant industry is leading a bipartisan effort in the legislature to reinstate the requirement that restaurants pay the difference if any server doesn't make minimum wage after tips.

Opponents of raising the minimum wage give various reasons for wanting to change the new wage laws: Voters didn't realize what they were voting on; some of the ballot initiatives were unconstitutionally pieced together; others would unconstitutionally affect the state budget. But most of the opponents share a common theme: They don't think raising the minimum wage is, on the whole, beneficial for their state.

“Just because the voters have an opinion doesn't make it constitutional,” said Patrick Connor, director of the Washington branch of the National Federation of Independent Business. The group is working with a coalition of Washington farmers, restaurants and the state food industry to challenge the $13.50-an-hour minimum wage by 2020 that nearly 60 percent of Washington voters approved. They argue that the ballot initiative unconstitutionally grouped together several issues into one question. The first court hearing is set for April.

Supporters of minimum-wage increases counter that they're being attacked after they won the game.

“They're sore losers, so they're trying to make changes to the actual electoral process to consolidate their own power,” said Sarah Michelsen, director of the progressive advocacy group Arizona Wins.

Arizona progressives are fronting multiple battles to save their victory to raise the state's minimum wage from $8.05 an hour to $10 an hour. The Arizona Supreme Court heard arguments Thursday about whether the minimum wage initiative unconstitutionally fails to identify a funding source. There are at least six bills in the GOP-controlled state legislature that would make it more difficult for initiatives to get on the ballot and give the legislature the power to retroactively undo any ballot initiative.

Just months after they thought they were done, Arizona Wins launched a political-style campaign to rally voters again. Ads targeting specific state lawmakers feature a copy of the state Constitution going up in smoke. “This is the biggest defense campaign we've ever run,” Michelsen said.

Washington, D.C.-based advocacy group Fairness Project launched its own “Save the Wage” campaign Thursday to pitch in.

Minimum-wage advocates say they're learning the hard way that a multiyear, multimillion-dollar effort to raise the minimum wage (which describes the campaigns in Arizona and many other states) is apparently only half the battle.

“We really have to think about the long game after the win,” Michaelson said.

When left to voters, raising the minimum wage has had astounding success. Over the past 20 years, every statewide minimum-wage ballot measure except for two have passed.

The past few years have been high-water marks even for advocates used to success. In 2014, four states — Alaska, Arkansas, Nebraska and South Dakota — approved minimum-wage increases by ballot measure. In 2015 and 2016, politicians in California, New York and Washington, D.C., approved significant minimum-wage increases. The Democratic Party adopted a $15 nationwide minimum wage to its national platform in July.

In all four states where minimum wage was on the ballot in November, raising it received a higher percentage of the vote than that state's winning presidential candidate. Arizona's minimum-wage increase was the first progressive ballot initiative voters approved in two decades.

“There's no way we could have won a minimum-wage increase in Arizona by 17 points if we didn't have strong Republican and independent support for it,” said Jonathan Schleifer of the Fairness Project.

But as minimum-wage victories have piled up, so has the opposition. In 2016, minimum-wage advocates had to derail GOP-sponsored ballot initiatives to raise it by a lower amount than what they were proposing. In Arizona, advocates survived months of court cases questioning their signature-collection strategy. Now, they're fighting in the courts all over again.

What's popular with the public isn't always the right thing to do, opponents argue. And if you have the ability to edit a ballot initiative after it's passed to better fit the industry affected, why shouldn't you?

That's what Greg Dugal of the Maine Restaurant Association says is happening in his state. After Maine voters approved an initiative to require restaurants to make up the differences in servers' tips (alongside a minimum-wage increase), the server community jumped into action to oppose it. They are lobbying the legislature to reinstate what's called the “tip credit,” arguing that customers are tipping them less because they mistakenly think their wages have gone up.

The bill has a shot to pass the Democratic-controlled State House and the Republican-controlled Senate. And in Maine, where the legislature has the power to change ballot initiatives, that's totally fair game, Dugal said.

Fair game or not, what lawmakers in Maine and Arizona — and the courts in Washington and Arizona — decide could reshape the minimum wage landscape just months after voters altered it.

This post has been corrected to make clear that Maine voters eliminated the tip credit and the restaurant industry is trying to reinstate it.