Miller's hiring comes the week after Corey Lewandowski was fired as Trump's campaign manager. He most recently worked on the presidential campaign of Sen. Ted Cruz (R-Tex.). He is a veteran of Capitol Hill and Republican congressional campaigns.
Alan Cobb, who has been a senior adviser to Trump, will serve as the director of coalitions, the campaign said. In that role, he will help organize and manage groups backing Trump, the campaign said.
Abboud will work on the campaign's rapid response and messaging.
Miller did not immediately comment. When Miller worked for Cruz, he was, like his then-boss, critical of Trump. The liberal group Think Progress published cached versions of some anti-Trump tweets deleted from Miller's Twitter account.