Ballot measures on abortion rights have succeeded beyond what even their proponents imagined when the United States Supreme Court overturned Roe v. Wade two years ago.

They have not only enshrined a constitutional right to abortion and restored access to the procedure in red and purple states. They have also converted what had been a voter mobilization advantage for Republicans into one for Democrats.

Now the strategy — and an unbroken winning streak — faces its biggest test ever, with 10 states asking voters whether to establish a right to abortion in their constitutions. On Friday, Nebraska became the final state to certify — it will be the only state with two measures, one sponsored by abortion rights supporters and the other by opponents.

Democrats, coming out of a convention where they highlighted reproductive rights like never before, are counting on the measures across the country to both expand abortion access and help them win in battlegrounds for the presidential race and control of the House and Senate, with key races in states including Arizona, Nevada and Montana.

And while voters have sided with abortion rights in all seven states where the question has appeared on the ballot since Roe’s reversal, this year’s map poses far steeper challenges, with citizen-sponsored abortion rights measures in five red states, two with near-total bans and all with aggressive opposition from Republican governors, courts or legislatures.

The ballot amendment in Florida alone will pose a test no other abortion proposal has faced: State law sets the threshold for passage at 60 percent, rather than a simple majority. In other red states, abortion rights groups have won with percentages in the high 50s.

And even proponents say victories in the ballot measures won’t necessarily deliver wins for Democratic candidates: Where measures have passed, they have outperformed Democrats on the same ballot, succeeding because voters have crossed party lines to support legalized abortion.

Still, the number of measures alone captures how the dynamic of the nation’s long abortion debate has shifted in the last two years.

This year, abortion rights groups have cleared an obstacle course of legal and logistical hurdles just to get on the ballot. Republican lawmakers and anti-abortion groups have tried to change the rules for certifying signatures and pass legislation that makes it harder to put the questions on ballots or pass them.

Proponents of an abortion rights measure failed in one state, Arkansas, on Thursday after the secretary of state said they did not submit proper paperwork regarding petitions circulated by paid canvassers. But elsewhere, abortion rights groups have set records for the number of signatures collected. In Arizona, one in five voters signed the petitions to place the measure directly before voters.

“It’s really hard to overstate how powerful this strategy has proven to be,” said Kelly Hall, the executive director of the Fairness Project, a nonpartisan group that supports ballot measures.

Abortion rights groups “have overcome not only the inherent difficulty of collecting hundreds of thousands of signatures, but also the manufactured difficulties that opponents of abortion rights have tried to throw at these campaigns,” she said.

In 2022, after abortion rights groups had early success — defeating all three anti-abortion measures in red states and winning the three that enshrined abortion rights in blue states — Ms. Hall urged caution, saying that ballot measures are expensive and hard to pull off.

Now, reproductive rights groups have put abortion rights amendments on the ballots of 11 of the 17 states that allow citizens to sponsor amendments — save three that broadly protect abortion access (Illinois, Massachusetts and Oregon) and three that have near-total bans (Arkansas, North Dakota and Oklahoma.)

“This is our best opportunity, it is maybe our only opportunity to use ballot measures as a tool, and we can win,” Ms. Hall said this week. “Now is the moment.”

Abortion opponents are sponsoring just one measure this year, in Nebraska, which would amend the Constitution to say that “unborn children shall be protected from abortion in the second and third trimester,” except in cases of rape or incest, or if the abortion is “necessitated by medical emergency.” Another group in the state failed to collect enough signatures for a stricter measure that would have banned abortion from conception.

A coalition of abortion rights groups is sponsoring a measure which, like those in other states, would protect a “fundamental right” to abortion until viability, or the point in pregnancy when a fetus can survive outside the uterus, generally around 24 weeks. Certifying the ballot measures on Friday, Nebraska’s secretary of state said it was the first time that two competing measures had appeared. If both pass, the amendment with more votes takes effect.

National anti-abortion groups have branded measures across the country “extreme” and “California-style” amendments, out of step with voters in more conservative states.

In one indication of their concern, Marjorie Dannenfelser, the president of Susan B. Anthony Pro-Life America, a prominent anti-abortion group, is leading a new political action committee trying to stop the Florida amendment from passing. Gov. Ron DeSantis, a Republican, has warned that the amendment succeeding “would be the end of the pro-life movement.”

“If only people that are pro-life oppose it, it very well might pass,” he told guests at a recent Tampa fund-raiser.

Appealing to voters’ unease with rare abortions late in pregnancy, the opponents say the amendments will allow “all trimester” abortions and take away basic safety measures and parental notification laws.

“Republicans will win if they emphasize support for pro-life protections, communicate on the issue with compassion, and contrast their position with the deeply unpopular Democrat agenda for unlimited abortion in the seventh, eighth and ninth months of pregnancy,” Kelsey Pritchard, the director of state public affairs for Susan B. Anthony, said in an email responding to questions about the ballot measures. (Almost all of the measures explicitly permit the state to restrict abortion after viability, except in cases where a treating health care professional says the procedure is necessary to save the life or health of the mother. And states that have passed ballot measures have maintained parental consent laws.)

Groups that tried and failed to stop the measures from making the ballots are now trying to shape official state documents that voters will see as they prepare to cast their ballots.

In Florida, a state panel largely appointed by Republicans approved a message to appear alongside the ballot amendment saying that the measure would result in “significantly” more abortions and fewer live births, which “may negatively affect the growth of state and local revenues over time.”

The Arizona Supreme Court, whose justices have all been appointed by Republican governors, upheld language in a state publicity pamphlet that will be sent to voters about the ballot amendment that uses the phrase “unborn human being,” the preferred term of anti-abortion groups for an embryo or fetus.

Democrats and abortion rights groups are urging the party to talk about abortion to recast Republicans as the party of control and theirs as the party of freedom. Democrats are particularly hoping to increase turnout among young women, who have shifted toward the party since the Supreme Court overturned Roe.

The party’s campaign committee in the House, which is looking to take at least four seats to win a majority, has identified 18 battleground races where they think abortion measures could help them defend or pick up seats. That includes two seats in Colorado, and five Republican-held ones in New York, where abortion is legal until viability but a ballot amendment would enshrine the right to decide one’s own “pregnancy outcomes.”

In Maryland, where access is similarly protected by state law, Democrats are hoping that a ballot amendment will help Angela Alsobrooks keep an open seat in the party’s column.

Abortion rights groups are most focused on states where the political goals coincide with the goal of restoring access. That puts particular weight on Arizona, where the Republican-led legislature, under pressure from voters, overturned a century-old ban on abortion, but another law prohibits it after 15 weeks of pregnancy. The state is a battleground in the presidential race, and Democrats think they have a shot at flipping two Republican House seats, and have to win an open seat to hang on to their razor-thin majority in the Senate.

Montana is no one’s idea of a presidential battleground, and a 1999 state Supreme Court decision has protected abortion access. But abortion rights groups say the amendment they are sponsoring is necessary to stop future courts from reversing the decision, as the Republican-led Legislature pushes to ban abortion. And Democrats are hoping it will motivate enough voters to re-elect Senator Jon Tester, the party’s most endangered incumbent.

In Nevada, state law allows abortion until 24 weeks of pregnancy, but Democrats hope the ballot measure that would enshrine that right in the constitution can help them win the state in the presidential election, and re-elect three House incumbents and Senator Jacky Rosen.

Missouri and South Dakota are not remotely competitive in the presidential or other federal races, but success on the ballot amendments there would restore access to the procedure and be hugely symbolic, the first time that citizens had directly voted to reverse a near-total abortion ban.

In Florida, a yes vote on the measure would nullify a six-week ban that has cut off abortion access for women not only in the state but across the South.