COLUMBUS (AP) — A hastily called summer special election over a Republican-pushed measure that would make it harder for Ohio voters to pass future constitutional amendments, including one on the November ballot to guarantee abortion rights, has driven off-the-charts early turnout before Tuesday's final day of voting.

Early turnout has been so heavy that some election offices are straining to manage the load and trying to recruit additional poll workers.

"This is gubernatorial-level turnout," said Regine Johnson, deputy director of the board of elections in Stark County. As of Thursday, the board was about 100 volunteers short of the number it targeted as the minimum to be fully staffed.

The early signs of a highly motivated electorate follows robust turnout in a handful of other states where voters have affirmed abortion rights after the U.S. Supreme Court overturned Roe v. Wade a little over a year ago.

Issue 1, the question before Ohio voters on Tuesday, was placed on the ballot this spring by the Republican-controlled Legislature. The measure does not specifically deal with abortion. Instead, it would erect several hurdles for voters to pass amendments to the state constitution, including raising the threshold to pass an amendment from a simple majority to 60%.

But if Issue 1 passes, it could be fatal to an amendment seeking to ensure the constitutional right to abortion that already is on the November ballot. In the 2022 midterm elections, AP VoteCast found that 59% of Ohio voters said abortion should be legal in most or all cases, just shy of that 60% mark.

Calling a special election in the middle of summer vacation season was seen by some as a cynical move because Republicans had just eliminated August elections with legislation signed into law only recently — specifically because those elections have historically generated such low turnout.

Not this time.

As of Wednesday, more than 533,000 people had voted by mail or in-person since early voting began July 11, according to data collected by The Associated Press. That's nearly double the final early voting figures for Ohio's two previous midterm primary elections, which included races for governor and Congress. In the May 2022 primary, for example, 288,700 people voted early, according to AP data.

It's also more than three times the roughly 142,000 early ballots cast by mail or in-person during last year's August elections, although drawing a comparison is tricky. August special elections traditionally have been held in even-numbered years and are intended for local races and issues. The last statewide question on an August ballot in Ohio was in 1926.

Voters have been waiting in long lines and sometimes for over an hour at many early polling places, even as heat waves have swept the Midwest and the rest of the country this summer. Tom Simmons of Clintonville, just north of the capital, Columbus, stood in line on a sunny Thursday morning and said he planned on voting in favor of Issue 1.

"I don't think purely partisan politics should change amendments," Simmons said.

In his view, a 60% threshold would encourage more bipartisanship on hot-button topics.

The polarizing battle over abortion in the state, with the constitutional amendment seeking to protect reproductive rights before voters in the fall, has driven the narrative for the campaigns supporting and opposing Issue 1. Both sides have invested heavily in get-out-the-vote strategies.

Voters do not register by political party in Ohio, but data from L2, a political firm that tracks early in-person and mail voting, indicates that Democratic-leaning voters are turning out in higher numbers than Republican-leaning ones.

As of Tuesday, voters identified by L2 as Democrats had cast more than 52% of ballots, compared with 40% by voters identified as Republicans. Independents cast the remaining ballots, according to the firm, which models party affiliation using the partisan primary a voter most recently participated in.

So far, women are turning out in higher numbers than men, according to L2.

Sheila Harrell, from the Columbus suburb of Westerville, voted against Issue 1 on Thursday — a decision heavily influenced by the upcoming November vote on abortion rights.

"As a woman, you should have that right," Harrell said, adding that parents also should be able to seek abortion care for their children in Ohio instead needing to travel for it. She recalled a case that generated nationwide attention last year, when a 10-year-old girl had to travel to Indiana for an abortion after being raped.

Sammi Cain of nearby Worthington also was voting early Thursday and said she planned to cast a "no" ballot. She does not see a need to change the state constitution and sees the measure as a way for Ohio's political leaders to stifle voters' voices.

Cain, a transgender woman and a veteran, believes her "no" vote is a way to make sure everyone, including people in the LGBTQ+ community, have equal rights.

"From my perspective, it looks like Republicans are just trying to take away the essential voting rights from literally the American people and they're going to try to consolidate as much power as they can, so I'm basically just trying to stop that," Cain said. "They're not just going to stop at abortion rights."

The voter motivation seen so far in Ohio is similar to what Kansas experienced a year ago, when it was the first state where voters weighed in on abortion rights since the Supreme Court ruling overturning Roe.

In that August election, voters in the Republican-leaning state affirmed abortion rights decisively. Voters rejected, by 59%, a proposed amendment to the state constitution to declare that it does not grant a right to abortion, which would have allowed lawmakers to greatly restrict or ban it.

More than 900,000 people voted in that primary election, nearly twice the number that turned out for a 2018 August primary. An aggressive grassroots campaign got Democratic and unaffiliated voters to the polls, quashing the usually Republican-heavy voting population but also gaining some support from GOP registered voters.

Elections officials across Ohio have been feeling the pressure of such a high-stakes election, especially after the Legislature abruptly reversed itself and called for the special election. In a tight 90-day time frame during what is usually a break period, county election boards have scrambled to train poll workers and find available polling locations.

Despite the heavy turnout and short window to prepare, several county officials said they feel ready for the election thanks to early planning.

In the first week of early voting, Franklin County's early polling place processed more than 1,500 voters a day. Since then, the number has more than doubled, said Antone White, director of the county's Board of Elections.

He said that number is likely to remain steady until Tuesday because the mail-in ballot deadline passed earlier this week. He thinks the final overall turnout may even surpass that of last November's midterm election.

"The scale has far exceeded our expectations," he said.