Campaign officials tell The Associated Press Huntsman will endorse Mitt Romney at an event in South Carolina on Monday morning.
The former Utah governor placed third in last week's New Hampshire primary despite devoting much of his campaign resources to the state. He had already acknowledged that expectations for him in South Carolina's primary this week will be "very low."
Huntsman was routinely at the bottom of national polls, barely registering at 1 or 2 percent.
The campaign officials spoke on condition of anonymity because Huntsman plans to make the official announcement Monday.