"Do you really think that he was urging people to kill Hillary Clinton? Do you really believe that?" King, a Trump supporter, asked Wednesday on MSNBC's "Morning Joe."
"No, I think he was just saying a dumb remark. It was as simple as that," King said. "Was he negligent in saying it? Absolutely. He should take it back."
King said Trump, the GOP presidential nominee, was not fully aware of what he was saying during his rally Tuesday and argued it was overblown to say Trump was suggesting Clinton, the Democratic nominee, be assassinated.
"To suggest that he was actually encouraging people to assassinate Hillary Clinton and use violence is wrong," King said.
"It's the type of comment a presidential candidate should not make."
The outspoken New York lawmaker continued to spar with the "Morning Joe" hosts throughout his appearance, which ended with him saying Trump has the temperament to be president.
Trump's campaign has been pushing back amid criticism over Trump's remarks Tuesday that gun owners could take action against Clinton.