NASHVILLE — President Trump is planning to focus his midterm campaigning this summer on red states with competitive Senate races where he has a deep reservoir of support and can bring a message devised to stoke partisan outrage.

The strategy is intended to take advantage of his star power among core Republican supporters while minimizing his exposure in states with competitive congressional races where his polarizing presence could help motivate Democrats as well as independents and moderate Republicans.

Mr. Trump’s appearance Tuesday in Nashville was an example of how he plans, for now, to campaign where he can have an immediate effect because of his ability to either fund-raise or draw local news media attention, according to White House officials who described the strategy on the condition of anonymity because they were not authorized to discuss it.

After a day in Washington, he flew to Tennessee to attend a fund-raiser and rally for Representative Marsha Blackburn, a Republican running for the seat being vacated by Senator Bob Corker, who is retiring. Ms. Blackburn has embraced Mr. Trump tightly in her bid in a state he won with more than 60 percent of the vote in 2016, and on Tuesday evening, crowds lined up in the streets around the old Nashville Municipal Auditorium, many wearing plastic slickers against pouring rain, to catch a glimpse of the president.