The final results from Tuesday’s voting are not in yet, but it’s already clear it’s been a great night for Rick Santorum. The former Pennsylvania senator has won the “beauty contest” in Missouri as well as the Minnesota caucus. Even if that turns out to be balanced by a win for Mitt Romney in the Colorado caucus, the day will still be judged a big win for Santorum. This will give him a big leg up over Newt Gingrich in the competition to be the leading “non Romney” in the GOP race. But if this means the beginning of the end for Gingrich, it may also concentrate the frontrunner’s attention on his surging conservative rival. If so, that may lead to a new round of ads and statements from the Romney campaign blasting Santorum.

But the assumption that a Romney “carpet bombing” of Santorum would achieve the same result as the attacks on Gingrich that have helped derail the former speaker’s presidential hopes is mistaken. Going negative on Gingrich merely reinforced the public’s doubts of the speaker’s character and record. To try and do the same thing against a candidate who has come across as the nicest guy left in the race might boomerang on Romney.

It should be conceded that there are plenty of avenues for criticism of Santorum. His defense of earmarks and his record as a “big government conservative” has the potential to alienate him from Tea Partiers. There are also real questions about his electability because he is so closely identified with hard line stands on social issues.

However, by staying out of the Gingrich-Romney mudslinging contest, Santorum has managed to bolster his image. The sympathy that was generated by coverage of his little daughter Bella’s illness also allowed him to carve out a unique niche in the race that put him above the fray in terms of roughhouse presidential politics. While Gingrich deeply resented the attacks on him from the Romney campaign, most Republicans know the former speaker has never shied away from smearing his opponents on either side of the aisle. To a certain extent, that knowledge protected Romney from intense criticism from many Republicans for going negative.

But if he tries the same tactic to take down Santorum, the blowback might do more damage to Romney than his intended victim. The spectacle of the frontrunner trying to demolish the character of another conservative rival may not go down well with the GOP grass roots, especially becauseSantorum has avoided the class warfare and personal attacks Gingrich launched at Romney.

An assault on Santorum may actually play into his hands, because it will make Romney appear like a bully trying to pick on the one candidate who has tried to run a clean campaign. Moreover, for all of Santorum’s vulnerability on financial issues, the longer the race has gone, the more likeable the Pennsylvanian has seemed. That’s the opposite of what has happened to Gingrich.

Romney needs to remember he still has an enormous advantage over Santorum. Nothing that happened on Tuesday night necessarily changes the narrative in which Romney cruises to the nomination. For Romney to initiate an all-out attack on Santorum would only inflate the senator’s image and make him appear unpresidential. Going negative on Santorum will be a terrible mistake that could help turn a Romney romp into a much more competitive race.