Maher was interviewing Nebraska Republican Sen. Ben Sasse on his HBO show Friday night when he brought up how adults in California dress up for Halloween. Sasse said that's frowned upon in his state and invited Maher to come ... and that's when the TV host dropped the N-bomb.
Maher was quick to tell the audience he was joking, but the backlash on social media was immediate.
Sasse has chimed in as well, saying he wish he's spoken up to Maher right away and asked him ... "Why would you think it's OK to use that word? The history of the n-word is an attack on universal human dignity ... Don't use it."
Maher has yet to respond.