The former Pennsylvania senator informed supporters of his plans during a Thursday night conference call. He’s expected to release a public statement Friday followed by a formal letter.
That’s according to a senior aide who isn’t authorized to speak publicly.
The decision is a formality that frees more than 200 delegates to support Romney at the party’s national convention next week in Tampa, Fla.
Santorum became Romney’s top opponent for the GOP nomination. His withdrawal from the race in April cleared the way for Romney’s general election fight against President Barack Obama.
Santorum won a total of 245 delegates during the primary, according to a count by The Associated Press.