Founded during the civil rights era to fight the Ku Klux Klan, the SPLC monitors extremist groups in America, a category that includes white supremacists, black separatists, neo-Nazis and the anti-government militia movement.
After two years of cataloguing an annual drop in the number of extremist groups in the United States, the 2015 report noted a 14 percent rise in the number of hate groups operating in America during the past year.
According to the report, groups identified with conservative extremism and with the black separatist movement have both grown over the past year. In absolute terms, the number of radical conservative groups monitored by the SPLC increased from 784 to to 892 last year, and the number of black separatist groups grew from 113 chapters to 180.
SPLC attributed the increase in black separatist groups to growing anger over the killing of black men by law enforcement officers, as well as institutionalized racism and other mistreatment and discrimination. Meanwhile, the campaign of Republican presidential front-runner Donald Trump bolstered the growth of conservative extremist groups, SPLC senior fellow Mark Potok wrote.
"Trump's demonizing statements about Latinos and Muslims have electrified the radical right, leading to glowing endorsements from white nationalist leaders such as Jared Taylor and former Klansman David Duke," Potok wrote. "White supremacist forums are awash with electoral joy, having dubbed Trump their 'Glorious Leader.'"
The billionaire "has repaid the compliments, retweeting hate posts and spreading their false statistics on black-on-white crime," Potok added.
A spokeswoman for Trump did not respond to a request for comment from The Huffington Post.
But the civil rights group isn't reserving its criticism exclusively for Trump. A SPLC report about anti-Muslim hatred also singled out GOP hopeful Dr. Ben Carson, who said last year that he did not believe a Muslim should be president of the United States. And fellow Republican candidates Ted Cruz and Jeb Bush supported banning Syrian Muslim refugees from entering the United States, while accepting Christian refugees, the report noted.
Along with an increase in radical anti-government groups and black separatists, the SPLC identified a marked rise in the number of Ku Klux Klan branches last year -- growth it said was likely linked to the debate over removing the Confederate flag from the South Carolina statehouse grounds after a white supremacist massacred black parishioners at a historic African-American church in Charleston.
Despite the storm clouds gathering over Republican politics, there was good news in the report, too. The once-powerful Aryan Nations group has all but disappeared, unable to recover from bankruptcy in 2000 and the death of the movement's founder, Richard Girnt Butler, in 2004.
The last self-proclaimed Aryan Nations leader, Morris L. Gulett, retired in November, saying that the movement "deserves to be respectfully laid to rest.”
As the report notes, "white supremacists have regrouped largely through Internet connections and forums, along with small in-person gatherings." Even so, the end of Aryan Nations is good news by any measure.
Editor's Note: Donald Trump is a serial liar, rampant xenophobe, racist, misogynist, birther and bully who has repeatedly pledged to ban all Muslims -- 1.6 billion members of an entire religion -- from entering the U.S.
Click here to read the SPLC's entire annual report, or view it below.