Republican presidential candidate Rick Santorum ended his campaign Wednesday and threw his support to Sen. Marco Rubio.
The former Pennsylvania senator finished 11th out of 12 candidates in the Iowa caucus.
In 2012, Santorum won Iowa and finished third in South Carolina.
He made his announcement during an interview with host Greta Van Susteren on Fox News’ “On the Record.”
Santorum said he decided, "The best way to do what I set out to do when we announced the run for president ... (is) by not furthering our campaign."
Of Rubio, Santorum said: "He's a tremendously gifted young man, he's a born leader."
Rubio responded, saying the endorsement "means a lot" to him.
"I have tremendous respect for Rick," Rubio said. "He's got a great agenda for blue-collar Americans — we need to grow our party among Americans that work hard with their hands everyday to make a living and move their families forward."
Santorum, 57, served in the U.S. House from 1991 to 1995, and the U.S. Senate from 1995 to 2007.
In the Senate, he worked on welfare restructuring, achieved a federal ban on a type of late-term abortion procedure and supported the war in Iraq, along with aggressive moves against terrorists abroad. Santorum now says the war was a mistake.
His conservative views on issues like gay marriage and abortion came under scrutiny when he ran for his fourth term in 2006, as did the fact that he spent little time in his Pennsylvania home. Democrat Bob Casey dealt him a crushing defeat.
Since leaving office, Santorum has been on the lecture circuit, penned several books and served as CEO of a Christian movie studio.
Santorum and his wife, Karen, have seven children.
The Associated Press and NBC News contributed to this report.