A pro-abortion referendum looked poised to win in the conservative state of Ohio this November. Now, Republican state legislators are accused of moving the goalposts.

Last summer, just like every summer for the past 22 years, Michael Curtin spent his days on the assorted baseball fields of central Ohio, acting as umpire for high school and college games.

Mr Curtin, retired after a 38-year career in journalism and another four in state politics, loves the game. But this summer, Mr Curtin’s umpire equipment has been neglected, shoved somewhere in the basement of his Columbus home so he could focus on the rules of Ohio politics instead.

“I’m not doing one game,” he said. “And I miss it. But this fight’s too important to lose.”

The fight in question is over Issue 1, a deceivingly dull and procedural-sounding referendum on the minimum threshold required to pass constitutional amendments.

The premise is simple: voters will decide on 8 August whether that threshold should remain at 50% plus one, or be raised to 60%.

But Ohio’s vote has become a proxy war over abortion, one of the many state-wide battles that have broken out since the US Supreme Court rescinded the nationwide right to abortion last June.

That’s because Issue 1 is not the only referendum looming. In November, Ohioans will vote on another constitutional amendment, one that would protect abortion access up until foetal viability, around 24 weeks of pregnancy.

The proponents of issue 1 claim that Tuesday’s vote is simply to protect the state’s constitution from outside influence.

But its opponents – a diverse coalition featuring political wonks like Mr Curtin, a retired Supreme Court judge and all of Ohio’s past living governors – have called foul. They claim Issue 1 is a backhanded attempt to change the rules mid-game, raising the voter threshold just in time to thwart the abortion vote.

“Look, everybody knows what’s going on here. Everybody knows,” Mr Curtin said. “This was just bad faith.”

Since Roe v Wade was overturned last June, the country’s abortion fight has increasingly played out in state ballot initiatives. There have been six so far, each one a win for abortion rights.

If Ohio’s vote is passed, it will be the most sweeping affirmation of reproductive rights in a state controlled by a firm Republican majority, said Mary Ziegler, a law professor at the University of California, Davis and a leading authority on the US abortion debate. “It will confirm that there’s some sort of consensus around abortion rights, even in conservative states.”

And according to recent surveys, if all Ohioans were to show up for the vote now, abortion would win. The constitutional amendment is supported by 58% of Ohioans, with 32% opposed, according to a July poll from USA Today and Suffolk University.

But if Issue 1 is passed first, and the threshold is raised to 60%, the abortion rights amendment may be finished.

“They [anti-abortion campaigners] very clearly looked at this and said: we cannot win if we don’t change the rules,” said Kellie Copeland, executive director of Pro-Choice Ohio.

Issue 1 has had the full-throated support of Ohio’s chief election official, secretary of state Frank LaRose.

“To allow a bare majority of 50% plus one to change the very ground rules that the state operates on is just not good public policy,” he told the BBC.

Mr LaRose, 44, is a veteran of the US Special Forces and now an enthusiastic envoy for the Republican Party, crisscrossing the state for more than 65 pro-Issue 1 events. He is charming, conservative and politically ambitious. In November – at the same time the abortion referendum is held – Mr LaRose will be on the ballot for the US Senate.

In public, Mr LaRose has kept the focus squarely on the constitution. But at a fundraising dinner in May, Mr LaRose made explicit the importance of Issue 1 for the anti-abortion movement.

“I’m pro-life. I think many of you are as well,” Mr LaRose said, in a video recorded by Scanner Media. “This is 100% about keeping a radical pro-abortion amendment out of our constitution. The left wants to jam it in there this coming November.”

In an interview with the BBC, Mr LaRose acknowledged that the “looming abortion amendment” helped bring the Issue 1 vote forward. “But that’s not the only reason,” he said.

To his opponents, Mr LaRose had been caught saying the quiet part out loud.

“There’s an old standard that our grandparents taught us that bears repeating: if you want any credibility in life… never deny the obvious,” Mr Curtin said. “Here is Mr LaRose denying the obvious.”

There have been other accusations of hypocrisy. Earlier this year, Republicans passed a law eliminating nearly all August elections, citing their high cost and low turnout. Then, in an apparent u-turn, they put Issue 1 on the calendar for 8 August.

Even some of Mr LaRose’s fellow Republicans have spoken out against Issue 1.

“You’re talking about changing a part of the Ohio constitution that has been in effect for well over 100 years,” said former Ohio Governor Bob Taft, a Republican. “And it’s worked, it’s worked well, the system is not broken.”

In the 111 years since Ohio first granted voters the power to introduce citizen-led amendments, just 19 of 71 proposed measures have passed. Ohio’s current policy requiring a simple majority is in line with most of the 17 US states that allow citizen-initiated amendments. And in 2015, Ohioans added a new restriction, passing an amendment that prohibited anyone from changing the constitution for their own financial benefit.

“This is an elaborate scheme to suppress the vote of Ohioans… It’s unconscionable,” said former Ohio Supreme Court Chief Justice Maureen O’Connor, also a Republican.

Whatever Mr LaRose’s motivations, Issue 1 has been embraced by Ohio’s anti-abortion lobby. Mike Gonidakis, president of Ohio Right to Life, said he “led efforts” to get signatures from state politicians to put the measure on the ballot.

“In speaking with Frank LaRose I said ‘now’s our time to do this’,” he told the BBC.

Mr Gonidakis, like Mr LaRose, rejected criticism that Issue 1 was underhanded. “It’s not changing the goalposts if Ohioans weigh in and vote on it,” he said.

Experts said they see Ohio’s Issue 1 as part of a broader tactic employed by anti-abortion advocates to circumvent public opinion in service of their ultimate goal, outlawing abortion entirely – a goal that is unsupported by most Americans.

“They think if voters had a straight up and down decision on abortion it wouldn’t go their way, so they’re trying to do what they can to prevent that from happening,” said the University of California’s Ms Ziegler.

As a result, anti-abortion leaders and their Republican allies have found paths around popular support – either relying on the court system or on politicians willing to promote abortion policy regardless of voters’ wishes.

These manoeuvres are possible, Ms Ziegler said, because in so many cases Republican politicians fear the anti-abortion lobby more than their own constituents.

And the strategy suits the movement’s internal logic, in which banning abortion is seen as the worthiest cause.

“There’s a sense in which winning is more important than democracy,” she said.