The number of hate groups in the United States rose for the fourth year in a row in 2018, pushed to a record high by a toxic combination of political polarization, anti-immigrant sentiment and technologies that help spread propaganda online, the Southern Poverty Law Center said Wednesday.

The law center said the number of hate groups rose by 7 percent last year to 1,020, a 30 percent jump from 2014. That broadly echoes other worrying developments, including a 30 percent increase in the number of hate crimes reported to the F.B.I. from 2015 through 2017 and a surge of right-wing violence that the Anti-Defamation League said had killed at least 50 people in 2018.

“We’re seeing a lot of bad trends,” Heidi Beirich, the director of the intelligence project at the Southern Poverty Law Center, said in an interview on Wednesday. “There are more hate groups, more hate crimes and more domestic terrorism in that same vein. It is a troubling set of circumstances.”

Ms. Beirich said the increase in extremist activity tracked by her team began in earnest in the early days of the 2016 presidential election, when anxieties over immigration helped propel President Trump to the White House. Before that, she said, the number of hate groups had fallen for three straight years.