Mitt Romney's rivals are casting doubt on whether he's the strongest candidate to take on President Barack Obama.
The Republican hopefuls sparred on a nationally televised debate Sunday.
Former House Speaker Newt Gingrich called the former Massachusetts governor's economic program "timid." Rick Santorum suggested Romney was a quitter who had walked away from his governorship rather than run for re-election.
Romney defended his record and said his business background would serve him well as president.
Gingrich pushed back at Romney's claim that he was not a politician, calling it "pious baloney."
Romney is strongly favored to win the New Hampshire primary Tuesday.