Former President Donald Trump refused at Tuesday’s debate to say whether he would veto a national abortion ban, as abortion is expected to be a central issue in the November election—and could particularly have an impact in several battleground states where the issue will appear on the ballot, including Arizona and Nevada.

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It’s not clear whether abortion ballot measures will significantly sway the presidential race. Analyses of past abortion measures have pointed out the questions typically outperform Democratic candidates, as some Republicans will vote in favor of protecting abortion rights but still vote for GOP candidates. It remains to be seen whether Trump’s refusal to say he would veto a national abortion ban could be enough to sway pro-abortion rights Republicans and independents in Arizona, Florida and Nevada away from Trump. A FiveThirtyEight analysis also argued ballot measures don’t necessarily boost turnout as much as Democrats have claimed, with data suggesting increased access to voting has a bigger impact than what’s on the ballot.

Ballot measures could have a bigger impact on state-level turnout when they’re designed to overturn existing abortion restrictions (like in Arizona or Florida) rather than when they reinforce the status quo (like in Nevada). Turnout increased in Michigan in 2022 when the state put a measure on the ballot that determined the legality of the procedure, for instance, with 4.5 million voting in 2018 versus 4.3 million in 2018 and 3.1 million in 2014. FiveThirtyEight attributes at least some of that bump to the state enacting same-day and automatic voter registration, though it notes the ballot measure’s fairly high stakes might’ve made it more impactful.

Beyond the presidential race, Democrats are also hoping an abortion-focused ballot measure in Montana will boost incumbent Democratic Sen. Jon Tester, as he faces a tough reelection fight in the right-leaning state. Maryland is also one to watch as Republican former Gov. Larry Hogan runs for the Senate in the typically left-leaning state, though Hogan has said he supports abortion rights. In its April memo, the DCCC identified 18 close House races in states with abortion measures in which Democrats could get a boost from the questions. More states have added ballot measures since that list was compiled, so there are likely even more races that Democrats are targeting now.

Abortion was a major topic at Tuesday’s debate, with moderator Linsey Davis asking Trump about whether he’d veto a national abortion ban after his running mate Sen. JD Vance, R-Ohio, suggested Trump would. The ex-president again pushed back on the idea of imposing a national ban and claimed “there's no reason to sign a ban because we've gotten what everybody wanted”—even as most voters oppose overturning Roe v. Wade—but refused to answer directly whether he would veto any ban that did pass. Trump said he “didn’t discuss” the issue with Vance, only claiming he “won’t have to” veto a bill and “we don't have to discuss it because she'd never be able to get it,” apparently referring to Harris wanting federal protections for abortion. Harris responded by slamming Trump’s defense of overturning Roe v. Wade and tied him to the impacts of the state bans, like people having to spend money to travel out of state for abortions or being denied IVF procedures, arguing, “What you are putting [people]

Trump has said he will vote against Florida’s abortion ballot measure in November even as he’s criticized the state’s six-week ban. When asked about his opposition to the measure at Tuesday’s debate, Trump falsely claimed the measure supports abortions “in the ninth month” and went off on a tangent about abortions in the ninth month and “after birth.” No state legalizes any procedure to kill babies after they’re born and abortions in later pregnancy are exceedingly rare, and Florida’s measure, if enacted, would only allow abortions up until the point of fetal viability—about 24 weeks—unless medically necessary.

It’s unclear how Trump’s position on abortion will continue to evolve before Election Day, as the ex-president faces backlash from his anti-abortion base for saying he supports abortion being left to the states and refusing to outright support a national ban. While Trump has disavowed a national ban—but remained vague on if he’d veto one—abortion rights supporters still believe it’s likely Trump would restrict abortion if elected, pointing to other steps Trump could take without a national ban, like enforcing the 19th century-era Comstock Act to ban mailing abortion pills and equipment or stripping abortion drug mifepristone of its federal approval. Trump has said in interviews he’s not interested in either of those options, but he has backed the proposals outlined in the Republican National Committee’s formal platform—which supports giving constitutional rights to fetuses, a legal theory that, if adopted, would ban abortion nationwide.

The Supreme Court overturned Roe v. Wade and the federal right to an abortion in June 2022, kicking off a wave of state bans nationwide. Polling has shown a majority of Americans support the procedure remaining broadly legal, however, which has led abortion to become a key election issue, as voters are inclined to support abortion rights. That’s led to Republicans often downplaying their opposition to abortion—even changing their campaign websites—in order not to alienate voters, and has made ballot measures a key tactic for abortion rights supporters, as they can harness voters’ support for abortion rights even in states where lawmakers want to ban it. Seven states have had ballot measures on abortion since the Supreme Court’s ruling—California, Kansas, Kentucky, Michigan, Montana, Ohio and Vermont—with all breaking in favor of abortion rights. Trump said in April he supported abortion being left up to the states after months of uncertainty of where the ex-president stood on abortion, and after he previously suggested he could be open to a national 15-week ban. Polling has suggested his position is broadly unpopular, with an August Kaiser Family Foundation poll finding 74% of women of reproductive age oppose leaving abortion up to the states, and anti-abortion advocates have decried Trump for not going further to oppose abortion rights.