Former President Donald J. Trump said in a video statement on Monday that abortion rights should be left up to the states, remarks that came after months of mixed signals on an issue that he and his advisers have worried could cost him dearly in the election.

Mr. Trump said his view was that the states should decide through legislation, “and whatever they decide must be the law of the land, and in this case, the law of the state.” But he added that he was “strongly in favor of exceptions for rape, incest and life of the mother.”

“Many states will be different, many will have a different number of weeks or some will have more conservative than others, and that’s what they will be,” Mr. Trump said in the video, which he posted on his Truth Social website.

“At the end of the day, it’s all about will of the people,” he added, falsely claiming that “all legal scholars” on “both sides” of the political aisle had wanted to see Roe v. Wade end. “That’s where we are right now and that’s what we want — the will of the people.”

Politically, Mr. Trump’s announcement that abortion should be left to the states will allow Democrats to tag him with some of the strictest abortion laws in the country, including a six-week ban in Florida that Mr. Trump has said was a “terrible mistake.”

That messaging began on X, the website formerly known as Twitter, by President Biden’s campaign aides shortly after the video posted. And Mr. Trump’s statement underscores that Republicans across the country are grappling with how to handle the issue of abortion since the Dobbs v. Jackson decision rolling back Roe v. Wade came down during 2022, a few months before the midterm elections.

In the video, Mr. Trump said he was “proudly the person responsible” for overturning Roe v. Wade, which eliminated the constitutional right to abortion after almost 50 years. Mr. Trump falsely claimed that “all legal scholars, both sides, wanted and in fact demanded be ended.”

He then claimed, falsely, that Democrats want babies “executed after birth.”

For months, Mr. Trump has debated with advisers what he should say about abortion to stop Democrats using the issue against him in November, as they did so successfully to outperform expectations against Republicans in the 2022 midterm elections.

Some anti-abortion activists had pushed Mr. Trump to support a federal abortion ban at 15 weeks, to set a minimum national standard and to block later term abortions in Democratic-controlled states.

As recently as February, Mr. Trump had privately told advisers he liked the idea of a 16-week national abortion ban with three exceptions, in cases of rape or incest, or to save the life of the mother, according to two people with direct knowledge of his deliberations. He made those comments as he was trying to fend off his last significant primary rival, Nikki Haley, in her home state of South Carolina.

He told his aides he wanted to wait until the Republican presidential primary contest was over to publicly discuss his views, because he didn’t want to alienate social conservatives before he wrapped up the nomination, the two people said.

Mr. Trump, who has approached abortion transactionally since launching his political career in 2015, told aides he liked the idea of a 16-week federal ban on abortions because it was a round number.

“Know what I like about 16?” Mr. Trump told one of these people, who was given anonymity to describe a private conversation. “It’s even. It’s four months.”

The Trump campaign called the reporting “fake news” at the time, but Mr. Trump then publicly made clear he was considering supporting a 15-week ban, and his advisers issued statements saying he would come up with a national consensus.

Democrats immediately pounced on the report of Mr. Trump’s plans, saying that Mr. Trump favored a national abortion ban. The blowback played a role in Mr. Trump’s decision to back away from announcing a national limit, according to people who spoke with Mr. Trump afterward. Some campaign advisers tried to distance Mr. Trump from the Times report about what he had been saying privately.

Mr. Trump described himself as “very pro-choice” late into adulthood before announcing he was “pro-life” as he considered running for the Republican nomination in 2011. In the 2016 election, Mr. Trump secured evangelical support by promising to choose his Supreme Court justices from a list of conservative judges who would be expected to favor overturning Roe.

But after the Supreme Court did what Mr. Trump engineered it to do, in June 2022, he told advisers the abortion issue could hurt Republicans badly in that year’s midterm elections. By the time the results were coming in — underwhelming for Republicans — Mr. Trump was privately discussing the abortion issue as if he were a television pundit, claiming credit for being right about how it would cost Republicans politically.

Mr. Trump was scathing in his private assessments of Republicans who he thought were overly “harsh” in their abortion positions, according to advisers. He often criticized two failed G.O.P. candidates for governor — Doug Mastriano in Pennsylvania and Tudor Dixon in Michigan — for being too hard-line on abortion and not allowing for sufficient exceptions.

Still, even as Mr. Trump has avoided taking a clear public position on abortion, he often highlights his role in appointing the three conservative Supreme Court justices who were pivotal to doing so.

Anti-abortion activists are hopeful that Mr. Trump will be as willing to allow them to shape policy in a second administration as he often did when he became president in 2017.

“You must follow your heart on this issue,” Mr. Trump said in his video. “But remember, you must also win elections to restore our culture and, in fact, to save our country, which is currently and very sadly a nation in decline.”

Michael Gold contributed reporting.