The conservative presidential hopeful said walking away now would be like the Kansas basketball team giving up in the first half, when it trailed by more than 10 points Saturday night against Ohio State, before rallying to win and advance to the NCAA title game.
"Look, this race isn't even at halftime yet," Santorum told "Fox News Sunday."
Santorum faces an uphill battle for the nomination. With about half of the GOP nominating contests complete, Romney has won 54 percent of the delegates at stake, putting him on track to reach the threshold 1,144 national convention delegates in June.
Santorum, a former Pennsylvania senator, who has won 27 percent of the delegates at stake, would need to win 74 percent of the remaining delegates to cinch the nomination.
Santorum acknowledged on NBC's "Meet the Press' that the Wisconsin vote will send a "strong signal" about the direction of the Republican contest.
But he also dismissed the notion that a prolonged primary would harm the party's chances against President Barack Obama in November. Santorum says GOP establishment figures are making that argument to convince voters that "they need Mitt Romney shoved down their throats."
Santorum said on Fox that Romney "hasn't painted a positive vision of this country. He hasn't been able to close the deal with conservatives, much less anybody else in this party. And that's not going to be an effective tool for us to win this election."
Romney was given a boost on Friday when Wisconsin Rep. Paul Ryan endorsed him, and then Sunday, first-term Sen. Ron Johnson, R-Wis., also said he was backing the former Massachusetts governor.
Ryan, the Republican chairman of the House Budget Committee, said Sunday that he thinks Romney has a good chance of winning a lot of delegates in Wisconsin.
"I think conservatives should coalesce around the Romney campaign and move on to the general election. And I hope a big victory on Tuesday will do just that," Paul said on ABC "This Week."