CBS

The Republican presidential candidates are focusing on South Carolina ahead of Saturday's primary.

Mitt Romney, with wins in Iowa and New Hampshire behind him, leads the GOP pack, but admits winning the state won't be easy. His opponents have joined forces to slow the frontrunner's momentum, attacking Romney on everything from his 15 years at a private equity firm to cruelty towards a family pet.

Newt Gingrich in particular has grabbed onto an old Romney anecdote regarding his dog, Seamus, riding in a kennel on top of the family vehicle for a 12 hour drive, and has used snippets of Romney discussing the incident in a new video titled "For the Dogs."

Gingrich has also put together a montage meant to depict Romney as a soulless and out of touch with the general public, using footage of Romney missteps such as a comment that he "likes to fire people" who provide him poor service, and arguing passionately on the behalf of corporations' personhood.

Other candidates such as Rick Santorum, who came within eight votes of Romney in Iowa, are depicting Romney as a moderate in an attempt to shore up the social conservative vote.

The winner of the South Carolina primary has become the nominee in every presidential election since 1980.