Representative Steve King, Republican of Iowa, questioned the historical contributions of nonwhite “subgroups” during an appearance on MSNBC on Monday, igniting swift backlash online.

Mr. King spoke during a panel discussion, led by the MSNBC host Chris Hayes, about the racial makeup of the Republican Party on the first day of the party’s convention.

“If you’re really optimistic, you can say this was the last time that old white people would command the Republican Party’s attention, its platform, its public face,” Charles P. Pierce, a writer at large at Esquire magazine, said during the panel discussion.