Supporters of a ballot measure that would enshrine abortion rights in the Ohio Constitution far outraised their anti-abortion opponents in the months leading up to the November election, bringing in nearly $29 million from donors since Sept. 8, the campaign’s latest filings show.

The effort against Issue 1, which would amend the constitution to protect abortion rights, raised just under $10 million in the same period, according to Thursday’s filings.

The largest donations backing the amendment since Sept. 8 came from out-of-state groups, including three gifts totaling $5.3 million from the progressive Sixteen Thirty Fund, based in Washington, D.C. The Sixteen Thirty Fund counts among its funders Hansjörg Wyss, a Swiss billionaire who has given the group more than $200 million since 2016.

READ MORE: Survey finds that abortions in the U.S. rose slightly overall after new restrictions started in some states

The campaign, known as Ohioans United for Reproductive Rights, also received $3.5 million from the New York-based Open Society Policy Center, a lobbying group associated with the billionaire philanthropist George Soros, and $2 million from the American Civil Liberties Union, also based in New York. Billionaires Michael Bloomberg of New York and Abigail Wexner, the Ohio-based wife of retired Limited Brands founder Les Wexner, each gave $1 million.

The campaign against Issue 1, called Protect Women Ohio, accepted more than half its donations in the final months of the race from Protect Women Ohio Action Inc., a committee associated with the anti-abortion group Susan B. Anthony Pro-Life America.

Protect Women Ohio’s other high-dollar donors included the Ohio-based Knights of Columbus, a Catholic fraternal organization, and the Diocese of Columbus.

The massive flow of out-of-state cash to the campaign supporting the amendment reflects the enthusiasm with which major donors nationwide have spent to protect abortion rights since the U.S. Supreme Court overturned Roe v. Wade, said Leslie Lenkowsky, a professor emeritus in public affairs and philanthropic studies at Indiana University.

It’s been harder for campaigns against abortion rights to get traction, Lenkowsky said. In Ohio, an August special election that would have swayed November’s election went in the direction of abortion rights supporters, which likely made anti-abortion donors less willing to keep giving.

READ MORE: How Missouri doctors are meeting a post-Roe demand for vasectomies

The fundraising edge abortion rights supporters have in Ohio is reflected in ad buys: Abortion rights groups are on track to outspend anti-abortion groups by about $7 million through Election Day on Nov. 7, according to AdImpact, which tracks spending on campaign ads.

Amy Natoce, press secretary of Protect Women Ohio, criticized the pro-Issue 1 campaign’s outside funding in a statement to The Associated Press.

“It’s no surprise the ACLU is dumping millions of dollars into Ohio to cement its radical anti-parent amendment in our constitution,” she wrote. “Whether voters are pro-choice, pro-life or somewhere in between, Issue 1 goes just goes too far and is too radical for Ohioans.”

Natoce’s statement also pointed out that the campaign supporting the amendment received a donation from Martin Haskell, a retired Ohio physician who debuted an abortion procedure that was once used for abortions later in pregnancy but hasn’t been legal in the U.S. for over 15 years.

Ohioans United for Reproductive Rights didn’t immediately respond to requests for comment.