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.
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