Former President Donald J. Trump will campaign on immigration and border policy today with events planned in Michigan and Wisconsin, two crucial battleground states in the Midwest.

Mr. Trump and other Republicans are trying to keep voters’ attention on the border as President Biden and Democrats, bolstered by a pair of court rulings out of Florida on Monday, grow more optimistic about their ability to center the campaign on abortion.

On Monday afternoon, the Florida Supreme Court overturned decades of precedent in ruling that the State Constitution did not protect abortion rights, allowing a six-week ban to take effect. But it simultaneously ruled that a proposed constitutional amendment to guarantee abortion rights until fetal viability could go on the ballot in November.

That means Floridians will be voting directly on abortion after living with a near-total ban for several months — which Democrats hope will increase turnout and give them a fighting chance in a state that has become increasingly favorable to Republicans.

Wisconsin is one of several states with presidential primaries on Tuesday, and its voters will also decide on two ballot measures after the state’s Republican-led Legislature proposed changing the State Constitution to restrict private funding and staffing of election offices.

Connecticut, Rhode Island, New York are also voting. Mr. Trump and President Biden have already clinched their nominations, though, so the outcomes of today’s primaries are not in doubt. Delaware even canceled primaries it would have otherwise held today.

But a small but significant resistance to their candidacies lingers in their respective parties. Nikki Haley, who dropped out of the race early last month, took nearly 18 percent of the vote against Mr. Trump in the Arizona primary two weeks ago. About 13 percent of Democratic voters have voted against Mr. Biden in the primaries so far, choosing either an “uncommitted” ballot option or voting for other minor candidates.

Mr. Biden won both Michigan and Wisconsin in the 2020 election, and Mr. Trump’s Tuesday trip to Grand Rapids follows a weaker-than-expected performance in the Michigan primary against Ms. Haley. Grand Rapids was an urban stronghold for Ms. Haley in that race, with more than a third of residents in Kent County backing her. Mr. Trump’s second event in the day takes place in Green Bay, Wis.

Activists in New York, Rhode Island and Wisconsin have urged voters to back primary protest votes as a way of registering their disapproval with Mr. Biden’s handling of the war in Gaza. The president has made some efforts to mend the damaging rift in the Democratic Party on the war, scaling back the full-throated support of Israel’s military operations that he had offered in the early days of the conflict.

Yet that has done little to quell the protest effort against Mr. Biden in upcoming primaries. And Heba Mohammad, a spokeswoman for a group that is pushing for the uncommitted vote in the state, Listen to Wisconsin, said there was no scenario in which she would vote for Mr. Biden in the general election.

“I think the only person here who is making it possible for Donald Trump to win is Joe Biden himself,” Ms. Mohammad said in a local television interview. “He’s not taking our demands seriously.”

Mr. Trump, meanwhile, has criticized Mr. Biden’s handling of the war in Gaza but has said nothing of substance about what he would do differently if he were president. He has also said that any Jew who votes for Democrats hates Israel and their religion.