Throughout the campaign, Romney waged a 'War of Attrition'. With an early lead he could afford to go at ease in some unfavorable states and pay more attention to the others. With a staggering financial base, he could outspend all his challengers in the states at which he decided to give a fight. He could also wage a longer campaign if necessary, a luxury not enjoyed by all his challengers. It is true that Romney fared badly in the conservative heartland. But, it is also true to say that his challengers have failed to defeat him in the more moderate turf.
Romney was helped by Gingrich to defeat Santorum in some close contests by diverting some votes from the conservative Pennsylvanian. After Santorum pulled out of the race, one may wonder if the other contender, Ron Paul, may have a detrimental effect on Romney's campaign. Hardly so. The fact that 'the permanent underdog' Ron Paul is doing better than Gingrich in some states even after Santorum's exit speaks volumes of Gingrich's inability of defeating Barack Obama if he was to become the eventual Republican candidate. Gingrich may have hoped to garner the support of delegates won by Santorum in the Republican Party convention and defeat Romney there. But with such poor performances, he doesn't have a realistic chance of doing so.
Therefore, partly due to the timely assistance of Gingrich and Ron Paul, Mitt Romney is in a position to begin the campaign against his next opponent, Barack Obama. For the Republicans, moderate or conservative, he is the best candidate to have. Being a Mormon, Romney may appear a non-believer to evangelical conservatives. But, to them Obama is even a worse 'non-believer'. A conservative will find it difficult to divert Obama's votes towards the Republican camp. Romney, with his business background, may hope to do so. Therefore, he is more likely to challenge Obama in the swing states and even in supposedly Democratic states.