Abortion will be on the ballot in 10 US states for the November 5 election, including battleground states that will play critical roles in the presidential race and the fight for control of Congress.

Democrats, led by Vice President Kamala Harris, the party's presidential candidate, have sought to build support for the measures, which they hope will galvanise left-leaning and independent voters. Harris faces Republican former president Donald Trump in the election.

The states where voters will decide whether to guarantee abortion rights include Arizona and Nevada, which are not only among the swing states likely to decide the presidential contest but also feature high-profile Senate races that could determine which party controls that chamber.

The issue of abortion has bedevilled Republicans since the US Supreme Court's 2022 decision to eliminate a nationwide right. Anger over the ruling was widely credited with limiting Republican gains in the 2022 midterm elections, as well as boosting Democrats performance in state races in Kentucky and Virginia last year.

Voters have chosen to protect or expand abortion access in all seven statewide ballot measures put to a vote since the court's decision, including in conservative strongholds such as Ohio, Kentucky and Kansas.

Here are the states where abortion will be on the ballot on November 5.

ARIZONA

Arizona election officials approved a ballot measure that would amend the state constitution to guarantee abortion rights up to fetal viability, generally considered to be around 23 or 24 weeks.

Abortions in Arizona are currently subject to a 15-week ban that Republican lawmakers passed in 2022 after the US Supreme Court decision.

President Joe Biden narrowly won the state over Trump in 2020, the first Democrat to carry it in 24 years, and polls show it is once again a close contest between Harris and Trump.

The state's race for an open Senate seat between Democrat Ruben Gallego and Republican Kari Lake is one of a handful expected to determine which party controls the Senate.

FLORIDA

The state Supreme Court on April 1 approved a ballot measure, backed by reproductive rights groups, asking voters whether to amend the state constitution to protect abortion access.

As of May 1, abortions in Florida are banned after six weeks with only rare exceptions under a law backed by Republican Governor Ron DeSantis.

Unlike in most states, constitutional amendments in Florida must pass with at least 60% of the vote, a higher threshold of support than any statewide abortion measure has yet received. A New York Times/Siena College poll released in early October found the measure falling short, with 46% of voters in support, 38% opposed and 16% undecided.

Once a perennial battleground state, Florida has leaned Republican in recent elections, voting twice for Trump and reelecting DeSantis in a landslide in 2022.

Trump, a Florida resident, has said he will vote against the ballot measure, after initially appearing to suggest he would vote in favour.

NEVADA

State officials approved a referendum for November that would amend the state constitution to protect abortion rights, after a coalition of reproductive rights groups submitted enough valid signatures.

State law already offers similar protections, but adding them to Nevada's constitution would make it harder to roll those rights back. Voters would need to approve the measure twice this year and again in 2026 to amend the constitution.

Nevada is a battleground state in the presidential contest, while the Senate race between incumbent Democrat Jacky Rosen and Republican challenger Sam Brown is one of the most closely watched of 2024.

OTHER STATES

Voters in Missouri and South Dakota — both deeply conservative states where virtually all abortions have been banned — will also decide whether to add abortion rights to their state constitutions.

Nebraska voters will face two opposing ballot measures. One would add the right to access abortions to the state constitution, and the other would enshrine the state's current 12 week ban with exceptions for rape, incest and the life of the mother — in the constitution.

In the unlikely event that both measures pass, the one that gets the most affirmative votes would take precedence, according to state officials.

Montana and Colorado, two states where abortion has remained legal, also have ballot measures that would add abortion rights to their state constitutions. Under Colorado law, ballot measures need 55% support to pass.

Supporters say adding protections to those states constitutions would ensure lawmakers or courts could not limit rights in the future. Montana's Republican controlled legislature has sought to overturn the state Supreme Court's 1999 ruling upholding the right to abortion.

While not a presidential battleground, Montana has a highly competitive US Senate race this year between Democratic incumbent Jon Tester and Republican challenger Tim Sheehy.

Lawmakers in two other states have approved abortion-related amendments for November's ballot: New York and Maryland. In both states, abortion is already legal; the referendums would amend their state constitutions to add more protections.