Hastings was among the most outspoken, saying that Clinton's GOP rival Donald Trump "would destroy much of what is great about America. Hillary Clinton is the strong leader we need, and it's important that Trump lose by a landslide to reject what he stands for."

Also on the list of supporters was businessman and investor Peter Chernin, AT&T's senior executive vice president Jim Cicconi, IAC's Barry Diller, DISH Network co-founder Candy Ergen, BET founder Robert Johnson, Magic Johnson, BET CEO Debra Lee, Ted Lenses, Box CEO Aaron Levie, former Time Warner Cable CEO Rob Marcus, Facebook COO Sheryl Sandberg, Alphabet chairman Eric Schmidt and Entravision CEO Walter Ulloa.

Cicconi, who leads AT&T's government affairs and lobbying in Washington, said that he has supported every Republican presidential candidate since 1976.

"But this year I think it's vital to put our country's well-being ahead of party. Hillary Clinton is experienced, qualified, and will make a fine president. The alternative, I fear, would set our nation on a very dark path."

On Thursday, Trump noted the endorsement of former Defense Secretary Donald Rumsfeld.