Huntsman said the former Massachusetts governor gives the Republican Party its best shot at defeating President Barack Obama in the November general election.
After staking his candidacy on New Hampshire, Huntsman finished third in the primary there last week. He faced a likely defeat in South Carolina's primary on Saturday.
Huntsman's resume had suggested he could be a major contender for the GOP presidential nomination. But the former Utah governor and diplomat found a poor reception for his brand of moderate civility, which he had hoped would draw support from independents as well as Republican moderates.
Huntsman announced his decision Monday in Myrtle Beach, S.C.
