WASHINGTON — For the first time in five years, the number of hate groups in the United States rose in 2015, according to a new report from the Southern Poverty Law Center, a legal and advocacy organization that monitors extremist activity.

The number of such groups spiked 14 percent in 2015, a year characterized by levels of polarization and anger perhaps unmatched since the political turmoil of 1968, the center said in a report on hate and extremism released Wednesday.

Swelling numbers of Ku Klux Klan chapters and black separatist groups drove last year’s surge, though organizations classified as antigay, anti-immigrant and anti-Muslim saw small increases, too.

‘‘It was a year marked by very high levels of political violence, enormous rage in the electorate, and a real significant growth in hate groups,’’ said Mark Potok, author of the report.

The center said a number of factors incited that anger, including shifting demographics that largely favor nonwhites; immigration; legalized same-sex marriage; the rise of the Black Lives Matter movement; and the atrocities carried out by Islamic terrorists.

Intolerant language among politicians helped to normalize hate, the center argued. And while it also singled out other presidential contenders, the center — which conservatives criticize for casting too wide a net — stated that Donald Trump had ‘‘electrified the radical right.’’

The number of KKK chapters in America more than doubled from 2014 to 2015, rising from 72 to 190, according to the report.

Black separatist groups also multiplied, rising from 113 in 2014 to 180 last year, it said.