Santorum surrenders, but can Romney capitalize?

The polls in Pennsylvania were not looking pretty for Rick Santorum. Already familiar with the unpleasant feeling of being on the losing end of an advertising onslaught from Mitt Romney and his allies, Santorum faced more of the same as the contest turned to his home state.

As one Romney adviser made clear to me over the weekend, "If he wants a fight in Pennsylvania, he is going to get a fight."

It appears Sen. Santorum didn't actually want that fight. Instead, he opted to bow out of the presidential race before being forced to launch the sort of full-throated Pennsylvania campaign that may have done nothing but cement his status as someone unable to win the support of the voters who know him best.

Newt Gingrich and Ron Paul ostensibly remain in the race. But Mitt Romney's approach to vanquishing his opponents (first Rick Perry, then Gingrich, and now Santorum) is instructive about how he plans to take down a likable incumbent president.

Just as Mr. Romney had his Super PAC supporters taking to the airwaves in state after state to destroy his Republican competition, the presumptive GOP nominee will now have "American Crossroads" providing air cover in key battleground states. That effort begins tomorrow with an attack ad hitting President Obama on domestic energy production and his apparent inability to lower the price of gas at the pump.

The general election campaign between President Obama and Gov. Romney began in earnest last week, but now with Sen. Sanotrum officially out of the picture, Romney and his team and their allies can begin focusing full time on building a path to 270 electoral votes and victory in November. And, perhaps, the money that would have been used by Team Romney against Santorum in Pennsylvania can now be diverted into building campaign organizations in battleground states.

He will need it. In President Obama, Gov. Romney will not find an opponent so easy to vanquish. Their campaign warchests will likely be on par with each other,. and a new Washington Post/ABC News poll shows significant advantages for the president in terms of voters' favorable and unfavorable attitudes toward the candidates.

Still, beyond the money and organization, Romney showed one other strength throughout the nomination season that may prove even more valuable. For the last several months, the dominant narrative has been how conservatives refuse to embrace Romney. (And perhaps many of them still haven't fully done so.) But Romney remained largely unswayed by that. He clearly flexed his conservative credentials to woo the base, but he didn't resort back into the Romney from his 2008 campaign, trying to be all things to all people. He showed a discipline to resist altering his approach in response to the constant pundit chatter.

If he can manage to keep doing that in the general election, he may thwart many of Team Obama's plans to knock him off balance.