Republican presidential candidate Rick Santorum denounced the "gutter politics" of his opponents on Monday.

The former senator from Pennsylvania carefully avoided naming Republican rivals Mitt Romney and Newt Gingrich, but nonetheless directed a scathing condemnation of their campaigns, which he said is "devolving into a negative campaign."

"I'm sick and tired of candidates who think they have to do anything that's necessary — anything — to win an election," Santorum told more than 300 people packed into an auditorium at St. Charles Community College.

"We deserve better than the gutter politics that we've been seeing in this race," he explained.

Santorum's comments come as he turns his campaign away from a failing effort in Florida in hopes of regaining momentum in the Midwest. He won the opening GOP Iowa primary, defeating front-runner Romney by a narrow margin of 8 votes.

After spending "a stressful weekend" with his three-year-old daughter who has pneumonia, Santorum resumed his Midwest campaign while forecasting a political revival in states such as Missouri and Minnesota.

Santorum is the first Republican candidate to appear in Missouri in advance of its February 7 primary, which is essentially a statewide public opinion poll. The GOP will award its presidential delegates in Missouri through a series of caucuses that begin in mid-March.

Gingrich is not on Missouri's primary ballot, which could allow the grass-roots Santorum to compete directly against the machine-politician Romney.

The well-funded Romney has been building a network of prominent Republican endorsements in Missouri.