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MANCHESTER, N.H. - Mitt Romney has never looked stronger than he does today.

He's built up a huge lead in New Hampshire. The famously flat line of his support in Gallup polling is trending upwards. And, in South Carolina - SOUTH CAROLINA - the former Massachusetts Governor is leading the pack with almost 40 percent of the vote, while the only southerner in the contest - Texas Gov. Rick Perry - has fallen to 5 percent.

It's remarkable what an 8-vote victory over an underfunded and unknown candidate in Iowa can do to momentum.

The only question now: can anyone to stop him? And, will they use tonight's ABC/WMUR debate here in Manchester to do it?

The candidate with the most room to grow - and the most to lose tonight - is Rick Santorum. After watching the other conservative alternatives to Romney rise and fall, Santorum is sitting in the right place at the right time.

But, Santorum won't get a clean shot at Romney.

Instead, he's just as likely to have to defend himself against attacks from Ron Paul who is struggling to hold onto second place here in New Hampshire and is in the hunt in South Carolina.

In Nashua, N.H. Friday, Paul questioned Santorum's conservative credentials saying "four or five times he voted to raise the national debt, so that tells you how conservative he is."

The Paul campaign is also releasing an ad in South Carolina that calls Santorum "another serial hypocrite who can't be trusted."

So, with Paul and Santorum potentially engaged in battle, can Romney simply float above the fray?

That all depends on what Newt Gingrich and Jon Huntsman decide to do.

For Huntsman, who has staked his entire campaign on a strong finish here in New Hampshire, there should be some incentive for him to go on the attack.

Yet, given his poor standing in the polling in the state (he's at just 7 percent in the latest WMUR poll), it actually makes little sense for him to try and skewer the front-runner.

No amount of pushing or pleading or attacking is going to change the fact that three days out from a primary he's trapped in a tie for a distant third place.

The former Ambassador to China has done the hard sell in New Hampshire - the only problem is that no one is buying it.

If he wants to try again in 2016 - or even angle for a post in a Romney Administration - it does him no good to go all slash and burn.

Gingrich, meanwhile, is the wild card here.

We know that Gingrich loathes the way Romney has run his campaign, even branding him a liar in an interview before the Iowa caucus.

Since last Tuesday, however, the former Speaker of the House has toned down his rhetoric and has instead tried to make the distinction between his record as a "Reagan conservative" and Romney's "moderate Massachusetts" record.

So which Gingrich will show up on stage tonight at St. Anselm College? The angry attack dog, or the more cerebral professor?

Remember, Gingrich his own reputation to think about as well. If he is to have any chance of recovering his faltering campaign, he can't afford to be labeled as the bitter, sore loser.

In the end, Romney may once again benefit from a divided field of GOP candidates who are struggling to win the mantle of the consensus "anti-Mitt" alternative.