Voters in at least three US states have approved ballot measures in favour of abortion rights, ensuring access to the procedure within their borders after the US Supreme Court overturned Roe v. Wade.

Voters in the battleground state of Michigan passed a constitutional amendment known as Proposal 3 that enshrines the right to an abortion by nearly 55 per cent, according to Edison Research.

In California and Vermont, voters also approved adding abortion protections to their state constitutions.

Meantime, voters in deeply conservative Kentucky looked poised to reject a constitutional amendment that would have declared there was no right to abortion, just as Kansas voters had done in August.

The victories for abortion rights suggested that voters of all political stripes are baulking at the severe abortion restrictions that several Republican-led states have enforced since the US Supreme Court gutted federal abortion rights in June.

The outcomes of the ballot questions, particularly in a swing state like Michigan, could set the stage for future state campaigns to proactively reinstate abortion rights.

“Proposal 3’s passage marks an historic victory for abortion access in our state and in our country – and Michigan has paved the way for future efforts to restore the rights and protections of Roe v Wade nationwide,” said Darci McConnell, a spokesperson for the campaign supporting the amendment.

Proponents of the amendment convened in downtown Detroit for an election results viewing party on Tuesday evening.

The mood was jovial as the “yes” votes on the Michigan amendment outpaced “no” votes across the state.

Nicole Wells Stallworth, executive director of Planned Parenthood Advocates of Michigan, took the stage and spoke to the crowd that included Centre for Reproductive Rights CEO Nancy Northup, local county prosecutors, campaign canvassers and abortion clinic workers.

“We’re living in a time like none other,” Wells Stallworth said. “And as such, we needed a campaign like no other.”

Michigan currently permits abortion up through viability, around 24 weeks, but a 1931 law banning abortions is still on the books and could have potentially been enforced. The passage of the amendment now renders that law unconstitutional.

Michigan Reproductive Freedom For All, a coalition of reproductive rights and progressive groups, led the petition to get the amendment on the ballot.

The group then worked to persuade swing voters that getting an abortion should be a private decision, not one made by politicians. The campaign raised more than $US43 million, according to political spending tracker Transparency USA.

The campaign opposing the amendment, Citizens to Support Michigan Women and Children, pushed the message that the amendment was too extreme and that the state’s elected leaders should get to decide abortion regulations.

The campaign raised about $US17 million, according to Transparency USA.

-Reuters