For more than a decade, former President Donald J. Trump fueled his political rise with dark appeals to white Christian voters, warning of immigrants coming for their jobs and nefarious efforts to undermine what he describes as the country’s true heritage.

Now, facing a neck-and-neck race against the first Black woman to win her party’s nomination, Mr. Trump is branching out.

He has repeatedly accused migrants of poaching “Black jobs” and “Hispanic jobs,” which is inaccurate, according to labor statistics. He told Latino voters in Las Vegas that illegal immigrants were “totally destroying our Hispanic population.” He promised women in Pennsylvania he would “be their protector” and that they would no longer be “abandoned, lonely or scared” — a vow based on the hyperbolic premise that criminals who also happen to be immigrants are lurking around every corner.

For all the frequent laments about how left-leaning politicians divide the country through “identity politics,” it appears to be Mr. Trump in this race who is making the most explicit identity-based arguments for voters to support his policies.

“He’s way more explicit than most prior candidates with these explicit appeals to Black voters and Latino voters that pit their various identity groups against each other,” said Michael Tesler, a professor of political science at the University of California, Irvine, who cowrote a book about how Mr. Trump wields white identity politics. “There’s a unified grievance in terms of ‘I’m not getting my fair share.’”

Many of Mr. Trump’s blunt and dire entreaties have been greeted with condemnation, even mockery, for their clumsy invocation of race, gender and religion. Yet, in this final, frenetic stretch of the contest, they also represent a striking effort to expand the tent of economic, racial and cultural grievances that propelled him to the White House eight years ago.