A new poll on voters’ attitudes in the nation’s most competitive House races showed that when it comes to perceptions of racism, there are two Americas — one in which people of color are distressed by President Trump’s rhetoric and policies and another in which white Americans are far less convinced that there’s a problem.

Conflicting perceptions of racism have always existed and should be expected, but this year, the divide may shape the outcome of the midterm elections.

This poll, a survey conducted for the N.A.A.C.P. by the African-American Research Collaborative, Latino Decisions and Asian Decisions, analyzed the views of African-American, white, Latino, Asian-American and Native American voters in 61 of the nation’s most competitive midterm races. We found that African-Americans stand to play a key role in 21 of these races, making up from 7 to 24 percent of the voting-age population. In 31 of the key races, voters of color represent 20 to 78 percent of the voting-age population and are positioned to have a significant impact.

Based on this, we expect their perceptions of Mr. Trump’s racism and his party’s acceptance of it will motivate them to cast votes for Democratic candidates.