(CNN) -- While Rick Santorum and Newt Gingrich can sustain their bare-bones insurgent campaigns long enough to fight through the spring, GOP frontrunner Mitt Romney and President Barack Obama have already moved on to the next battlefield.
Earlier on Tuesday, less than a day after his campaign released a tough anti-Romney attack ad labeling him as the candidate of Big Oil interests, Obama criticized the former Massachusetts governor by name for the first time this year, taking a swipe at his support for Rep. Paul Ryan's budget plan.
Romney himself has turned up the heat in recent days, telling voters the president is personally responsible for high gas prices. After his decisive victories in the Maryland, Wisconsin and the District of Columbia primaries, Romney fired back Tuesday night in a speech that didn't mention any of his Republican rivals.
"(Y)ears of flying around on Air Force One, surrounded by an adoring staff of true believers telling you what a great job you are doing -- well, that might be enough to make you a little out of touch," Romney said.
Granted, some of the same weak spots that have plagued the former Massachusetts governor throughout the primary season popped up again on Tuesday.
Exit polls in Wisconsin, a major swing state this fall, suggest he still hasn't made the sale with some working-class voters, rural voters or evangelicals. One in three Republican primary voters in the state said they wouldn't be satisfied with Romney as the party's nominee.
Six in 10 Wisconsin voters looking for a "true conservative" backed Santorum -- more than four times the number who backed Romney.
However, all of those issues are possible fall challenges, not potential nomination hurdles. Four in five Wisconsin voters said they think Romney will be the nominee.
Romney may have struggled with the state's most conservative voters, but thanks to a relatively low evangelical contingent, he still squeaked out a narrow win over Santorum with that group.
Santorum appears to have gained some late momentum with a double-digit advantage among late-deciders. However, it wasn't enough to blunt Romney's momentum as he pivots further from primary season battles to an increasingly likely fall faceoff.