Republican presidential candidate former Pennsylvania senator Rick Santorum speaks at the First National Bank Exhibition Hall in Loveland, Colo., Saturday. (Chris Schneider/AP)

"Now, we're getting to the states where people don't have the natural advantage, don't have the time commitment, the staff commitment to really build out an organization like they did in these first five," Santorum said in an interview on "Fox News Sunday."

"I think we're going to do very well here in Minnesota. I think we're going to do very well in Colorado, and we've got a one-on-one match up against (former Massachusetts governor) Mitt Romney in Missouri, while there's no delegates, it is a key state, it is a primary. And we think we can do exceptionally well in the state of Missouri."

Colorado and Minnesota both hold their caucuses Tuesday; Missouri, meanwhile, holds a non-binding primary.

Asked by host Chris Wallace whether the upcoming trio of states will be "make or break" for his campaign, Santorum said they would not -- and took a shot at Romney and former House speaker Newt Gingrich as "flawed" candidates.

"Oh, no, not at all," Santorum said. "I think we're going to show improvement. This race is a long, long way from being over.. . . We have two candidates candidly that are flawed. If you look at Florida and Nevada, the results were down as far as participation is concerned. I mean, this is not a good sign when the two candidates that everybody is talking about are not generating any energy in the Republican primary."


Republican presidential candidate Rep. Ron Paul (Texas), waits backstage before at a campaign stop Saturday, in Rochester, Minn. (Charles Rex Arbogast/AP)

"Well, you know, it's hard to say exactly when, but we have three or four caucus states that we believe our numbers are doing pretty good, so we have to just wait and see and continue to do exactly what we're doing," Paul said.