Debates have been the device that enabled Newt Gingrich to salvage his candidacy during the fall and then to revive it again earlier this week after a strong performance put him back into contention in South Carolina. But with most of the recent polls now showing Gingrich having vaulted into the lead in that state, the pressure is on Mitt Romney to do something in tonight’s debate that will reverse the momentum the former speaker of the House has created in the last few days.

Unlike his GOP rivals who have concentrated their fire on his record, Romney has focused most of his remarks in the debates on Barack Obama; the man he assumes will be his opponent in November. But with his South Carolina lead having evaporated and all eyes on the rhetorical dustup in Charleston to be broadcast on CNN tonight, Romney will be tempted to go on the offensive against Gingrich and echo some of the attacks his super PACs have used against the former speaker. However, that would be a mistake.

The accumulated effect of negative advertising and the consolidation of the conservative vote behind Gingrich as Rick Santorum faltered and Rick Perry dropped out appear to have completely erased the lead Romney had amassed in the Palmetto state. That will increase the sense of urgency tonight for Romney as he needs to both avoid falling further behind and to somehow dent Gingrich’s armor. Yet a change of style would be disastrous for the former Massachusetts governor. If he acts in such a way as to lead viewers to sense he no longer believes he has the nomination in the bag, it would be the worst possible outcome for Romney.

While Romney has on the whole done a creditable job in the debates, it may be asking too much to expect him to halt what appears to be a Gingrich surge to victory in South Carolina. Although it seemed likely he could wrap up the nomination with a victory there, Romney need not despair even if Gingrich wins. Though Gingrich can expect a boost from such an outcome, Romney is unlikely to lose the huge lead he has established in Florida, the next state to hold a primary. Just as the other candidates have maintained it will be a long battle, he has to remember he still has a big advantage in most of the states that have yet to hold elections. Romney has to keep his cool and maintain the demeanor of the man who is still the most likely to be accepting the GOP nomination in Tampa later this year.

With Rick Perry no longer on the stage, the four left standing on the debate stage will have even more opportunities to have at each other. Rather than Romney going on the attack, it will be Rick Santorum (whose hopes have taken the biggest hit this week despite the belated announcement of his victory in Iowa), who will have the greatest incentive to lash out at the others. But instead of honing in on Romney’s liabilities, the former Pennsylvania senator will probably talk more about Gingrich’s problems. And no one should be surprised if Santorum, who had hoped to ride evangelical support to victory in South Carolina, doesn’t stay away from Gingrich’s personal problems, which will be highlighted later in the evening when Marianne Gingrich, the speaker’s second wife, appears on “Nightline” to skewer her former husband.

If nothing else, these circumstances should make for good television in the latest episode of what has become America’s favorite political reality show.