For Democrats, the new rules could make it harder to raise the revenue they need to enact progressive reforms with tax increases on the wealthy.
Since winning control of 25 state legislatures in 2010, Republicans have successfully moved state level policy to the right. Democrats hope to pull it back left via victories in 2018 — but are worried that changes to state rules could put their agenda out of reach.
Florida's Republican lawmakers have approved a ballot measure that, if approved by the voters, would require a two-thirds "supermajority" of the legislature to enact any new taxes.
"It's very clear that they're getting ready for when they're out of power, and trying to stack the deck now as much as possible," said Tallahassee Mayor Andrew Gillum (D), who is running for governor on a platform of enacting Medicare for all and putting an additional $1 billion into education. "Everything we have proposed hinges on our ability to defeat this."
At least 14 states already have supermajority tax requirements, according to a 2017 tally by the National Conference of State Legislatures. They include some states that Democrats are hoping to take back this year, such as Wisconsin and Michigan.
In three additional states — Florida, Oregon and North Carolina — conservative lawmakers and business groups are currently advancing similar measures, said Meg Wiehe, a tax analyst at the Institute on Taxation and Economic Policy, a left-leaning think tank.
The supermajority requirements have proved effective at keeping taxes low in the states where they have been implemented, said Joel Griffith of the American Legislative Exchange Council, a group tied to the conservative billionaire Koch brothers.
Oklahoma has had its supermajority requirement for several decades, and it has hiked taxes only once — earlier this year, amid protests over tight education budgets — during that entire period, according to Griffith.
"These supermajority rules make policymaking incredibly difficult," said Elaine Maag, senior research associate at the Tax Policy Center, a nonpartisan think tank. "If a state can't increase spending because of these very high bars for raising taxes, they can't expand programs even if people in the state want them."
The supermajority requirements have also proven difficult to undo, since repealing constitutional amendments requires the voters to reverse their stance at the ballot box.
Such measures are not the only hurdle to enacting a single-payer health-care system at the state level; progressives already have to contend with centrist Democrats averse to tax hikes and Republican attacks over bigger government spending. But progressives say the supermajority requirements could make their policy vision virtually impossible to achieve, even if they win handily at the ballot box.
With backing from Gov. Rick Scott (R-Fla.), Florida's Republican-controlled House and Senate voted this spring to put the supermajority rules to the voters through a referendum in November. Most Democrats in both chambers voted against putting the supermajority rule to a ballot vote.
The proposal would need approval from 60 percent of voters to successfully alter the constitution. Florida already has a supermajority requirement for raising corporate taxes, but the new ballot measure would extend that requirement to other taxes as well.
"It should be difficult to raise taxes. We want to make it as difficult as possible," said state Sen. Rob Bradley (R), who helped push the measure onto the ballot.
In North Carolina, conservative groups have mobilized behind a ballot initiative to change the state's constitution to lower the maximum income tax rate from 10 percent to 7 percent. If approved by voters, the state government will not be able to lift taxes beyond 7 percent without a constitutional amendment.
"We really want to make sure the taxpayers of North Carolina are protected," said Chris McCoy, state director of North Carolina Americans for Prosperity, a right-wing advocacy group. "We're trying to make sure there's certainty in the market."
But others say the supermajority requirements create dysfunction and tie lawmakers' hands, particularly at a time when the federal government under President Trump has pursued policies that have pushed up the number of uninsured Americans.
"What they want to do is pass this measure now so they'll be able to jam a Democratic governor by forcing votes that will require Republican participation," said Gillum, the Florida Democrat running for governor. "We have to do everything we can to make sure this does not go through."