The political network created by the billionaire industrialist Koch brothers announced on Sunday that it was suspending its support for Nikki Haley in the presidential primary after her latest defeat in South Carolina.
The group, Americans for Prosperity Action, had spent tens of millions of dollars trying to elevate Ms. Haley and prevent the renomination of Donald J. Trump, but it had already slowed its spending in the G.O.P. race dramatically after Ms. Haley fell short in the New Hampshire primary last month. The organization made its decision official on Sunday.