The former Republican president, who has posted on his Truth Social account about the murder of 25-year-old Ruby Garcia in Grand Rapids last month, is due to make remarks in the city that his campaign has titled "Biden's border bloodbath." Police say Garcia was shot in her car by Brandon Ortiz-Vite, 25, who she was dating.

Peter Hoekstra, the chair of the Michigan Republican Party and a Trump ally, told Reuters he expects Trump to address Garcia's murder in his speech. Trump's campaign did not respond to requests for comment.

Trump is making the issue of immigrants crossing illegally into the U.S. from Mexico a centerpiece of his campaign. In recent months his rhetoric about migrants has become increasingly dehumanizing. He has called them "vermin" and "animals."

Trump and fellow Republicans have seized on Garcia's murder as an example of what they claim is Biden's failure to stem the flow of illegal immigrants into the United States.

Trump accused Biden in a speech in March of engaging in a "conspiracy to overthrow the United States" through lax security policies that have allowed millions of migrants to stream across the U.S. border with Mexico.

Polls show voters in both parties becoming increasingly concerned about the steady stream of migration.

Biden blames Trump for encouraging Republicans not to pass legislation in Congress this year that would have beefed up security at the southern border and introduced new measures aimed at reducing illegal immigration.

The Biden White House is also considering executive actions to reduce illegal immigration in the coming year, two U.S. officials and a third source familiar with the matter told Reuters in February.

"Donald Trump is engaging in extreme rhetoric that promotes division, hate and violence in our country," Michael Tyler, Biden campaign communications director, told reporters on Tuesday. "He encourages white nationalists and cheers on the disgusting behavior of the extreme far right."

Trump and fellow Republicans have also seized on the case of another young woman, Laken Riley, a 22-year-old nursing student from Georgia who was allegedly murdered in February by an immigrant who was in the country illegally and who had been released on parole.

Trump frequently claims without evidence that migrants have caused a spike in violent crime in U.S. cities.

TUESDAY'S PRIMARIES

Trump is also set to hold a rally with supporters in Green Bay, Wisconsin, after his Michigan speech. Michigan and Wisconsin are two swing states that could determine whether Biden or Trump occupies the White House next year.

In the 2020 election, Biden beat Trump in Wisconsin by less than one percentage point, and in Michigan by less than three. Both states, two of a handful of battlegrounds that will determine November's election, are expected to be extremely close again this year.

Although both Trump and Biden have mathematically clinched their presidential nominations, they will be on their party's presidential primary ballots in Wisconsin on Tuesday.

The Biden team will be watching for protest votes by Democrats angry over the president's support of Israel in its war against Hamas in Gaza.

In February's presidential primary in Michigan, a state with a large Muslim population, Biden easily won the primary but more than 100,000 Democrats voted "uncommitted", instead of for Biden, as a protest over his Gaza policy.

A similar option is available in Wisconsin on Tuesday, when voters can opt to mark their ballot for "uninstructed delegation".

The "uncommitted" campaign's goal in Wisconsin is to get 20,682 voters to mark their ballots "uninstructed," Wisconsin's version of "uncommitted." The number is significant. Biden beat Trump by that number in the state in 2020.

(Reporting by Tim Reid and Nathan Layne, additional reporting by Nandita Bose; editing by Ross Colvin and Stephen Coates)

By Tim Reid and Nathan Layne