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Still riding high off of his three-win streak in Minnesota, Missouri and Colorado last week, Rick Santorum blasted Republican rival Mitt Romney on Sunday, saying the GOP frontrunner was getting "desperate" by trying to paint Santorum as anything less than a true conservative.

"For him to suggest that I'm not the conservative in this race - you know, there's - you reach a point where desperate people do desperate things," Santorum told me on "This Week."

Santorum's comments were in response to statements Romney made earlier in the week that both Santorum and his fellow GOP rival Newt Gingrich are "Republicans who acted like Democrats."

"That's pretty funny for Mitt Romney saying I'm acting like a Democrat," Santorum said Sunday. "Another candidate has come up to challenge him, and this time he's having trouble finding out how to go after someone who is a solid conservative, who's got a great track record of attracting Independents and Democrats and winning states as a conservative."

Santorum said that despite his third place finish in the Maine caucus on Saturday, he expects to "do exceptionally well" in the Arizona and Michigan primaries the end of the month. The former Pennsylvania Senator his strong showing in the next two contests would make the GOP nomination a "two person race."

Santorum credited Romney's success thus far not to his policies or record, but to his fundraising prowess. Romney currently leads Santorum in the delegate count 105 delegates to Santorum's 71 delegates.

"He's been able to win in these early primary states by, you know, beating the tar out of his opponents by four- and five-to-one on television," Santorum said. "Well, of course, in the fall, he's not going to have the most money."