The move was "so sad," said Michael Reagan, son of Ronald Reagan and president of The Reagan Legacy Foundation.
He also said his "father would be so embarrassed" by the current situation.
@ReaganWorld: My father would be so embarrassed by this...I ask all who loved my father to vote down ballot to save the Country and Republican Party
Trump tweeted that his "team of deploarables" would be running his account during the event.
@realDonaldTrump: My team of deplorables will be taking over my Twitter account for tonight's #debate #MakeAmericaGreatAgain
Clinton said in a Facebook post that she has "no intentions of allowing [Trump] to hijack this debate, this election, or this country with his divisive rhetoric about people or groups of people he doesn't like."