But neither has found a wedge issue that undermines the front-runner. In Monday's debate Gingrich edged away from his attacks on Romney's business record. Santorum took the alpha male role over Romney in one heated interchange, but in support of a proposal -- voting rights for released felons -- not popular with South Carolina Republicans.
Romney has been the target of negative ads run on behalf of Gingrich, Santorum and Perry, and the pro-Romney super PAC has been running negative ads, as well. Santorum has been hit as a "big government conservative" in ads run Paul, who repeated his charge in the debate.
The debate moderators spoke of negative ads in disapproving tones, but South Carolina voters don't seem to mind. As South Carolina-born Andrew Jackson taught, if you believe in a cause, you should be willing to fight for it.
This can be carried too far. Perry, making a defensible point in the debate about federal intrusion on state issues, said South Carolina was "at war" with the federal government, which was once true but hasn't been since 1865.
Santorum more interestingly pointed to a Brookings Institution study that showed that almost everyone who graduates from high school, gets a job, and marries before having children stays out of poverty -- but that the Obama administration prohibits programs for at-risk girls from teaching abstinence or promoting marriage.
But this, like Gingrich's spirited and convincing defense of his proposal for janitorial work for high schoolers, did little to distinguish his policies from Romney's. The fact is that all three of these candidates, and Perry and Paul as well, have blemishes on their records from the perspective of tea party conservatives.
Except for Paul, they also have this in common: In opposing the Obama administration, they explicitly invoke the words and principles of the Founding Fathers. The debate riff that got a standing ovation was when Gingrich talked of "the pursuit of happiness."
That history evidently still resonates. In the Revolutionary War, unlike the 1860s, South Carolinians bet on the winner. They seem likely to do so again next Saturday.