With Win in Hand from La., Santorum Eyes Wis.

GREEN BAY, Wis. -- Another victory in hand but still badly trailing rival Mitt Romney, Republican presidential hopeful Rick Santorum vowed to continue his campaign despite an increasingly steep climb to the nomination.

Santorum, buoyed by Saturday's win in Louisiana's primary that boosted his spirit but did not narrow the delegate gap, urged his supporters to stick with him even as much of the GOP establishment has coalesced around Romney's increasingly inevitable coronation. Even in the face of the political headwinds, the former Pennsylvania senator seemed unwilling to acknowledge it would take a dramatic change in momentum to deny Romney his turn as the GOP nominee.

"You don't believe, as the pundits have said, that this race is over. You didn't get the memo," said Santorum, who won bragging rights in an 11th nominating contest but did little to shift the dynamics of the drawn-out race. "We're still here. We're still fighting."

But it's going to be a tough fight, for sure.

Romney remains far ahead with 568 delegates to Santorum's 273, according to an Associated Press tally. Newt Gingrich follows with 135 and Ron Paul has 50.

Short the 1,144 delegates it will take to clinch the nomination ahead of the convention this summer in Tampa, Fla., Romney enjoys an organizational and fundraising advantage over his closest rival. For instance, Santorum isn't even on the ballot for the primary in the District of Columbia, for its April 3 primary - the latest illustration of how the under-funded underdog struggles to keep pace with Romney's years-in-the-making campaign.

Earlier Saturday, Santorum said he wanted to debate Romney without trailing competitors former House Speaker Newt Gingrich and Rep. Ron Paul of Texas on stage.

"This race has clearly gotten down to two candidates that can win the nomination," Santorum told reporters in Milwaukee. "I'd love to have a one-on-one debate."

Romney's team, increasingly confident, dismissed the idea and the win.

"Rick Santorum is like a football team celebrating a field goal when they are losing by seven touchdowns with less than a minute left in the game," said Romney spokesman Ryan Williams, who crashed Santorum's victory party here.

Neither Santorum nor Romney, who took a day off from campaigning, was in the state as Louisiana Republicans weighed in. Both men were looking ahead at the upcoming contests, although the topsy-turvy race has proved unpredictable.

"This race is long and far from over, and to the people of Wisconsin, I just say to you: On, Wisconsin! Let's get it done!" Santorum told a sparsely attended victory celebration.

Santorum badly needed a rebound after a decisive Illinois loss to Romney earlier in the week that moved party stalwarts to rally around the front-runner. Many urged Santorum and Gingrich to drop out of the race.

Both refused, and campaigned aggressively in Louisiana in hopes that a victory there would justify them staying in despite Republican worries that the long nomination fight could hurt the party's chances against President Barack Obama. The Democratic incumbent faces no serious primary challenge and his re-election campaign already is well under way.

Santorum's improbable campaign was continuing Sunday, with a schedule that included a TV appearance and a busy day of campaigning in Wisconsin. Aides are looking ahead at the state as a bright spot, as well as Pennsylvania, the delegate-rich state Santorum represented in Congress.

But Romney's campaign is airing TV ads in the state, and his super PAC allies have plowed more than $2 million into TV advertising here. A crush of advertising - mostly negative - eroded Santorum's strength in states such as Michigan, Ohio and Illinois as he simply couldn't keep pace.

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Hunt reported from Washington, D.C.