The last time there was a presidential election, the country was coming off a summer of protests in favor of greater racial equality. Support for increased immigration was at the highest level ever polled.

This year is different. Former President Donald J. Trump’s campaign, filled with anti-immigrant rhetoric, is playing out in a country where researchers report seeing particularly high levels of hate speech against minority groups.

A spike that began soon after the George Floyd protests was sustained over four years and has only risen since Vice President Kamala Harris became the Democratic presidential nominee.

“I certainly don’t remember in my lifetime the rhetoric against immigrants ever getting this strong during an election,” said Yonatan Lupu, an associate professor of political science at George Washington University who leads a team that monitors about 1,000 hate communities across a range of online platforms.

Mr. Lupu said that hate speech levels were up about 50 percent compared with early 2020 before the murder of Mr. Floyd that summer.

Immigrants are reporting harassment and false accusations in communities from Aurora, Colo., to Springfield, Ohio. Extreme rhetoric against migrants has been amplified by Republican politicians and commentators, while the Israel-Hamas war has given rise to increased Islamophobia and antisemitism, including from the left.