Santorum: Romney "doesn't have a core"

Rick Santorum accused rival Mitt Romney of not having "core" beliefs and Republicans will ultimately pick a true conservative to take on President Obama in the fall.

Romney "is someone who doesn't have a core. He has been on both sides of almost every single issue in the past ten years," Santorum said in an interview on "CBS This Morning."

Romney has more than twice as many delegates as Santorum in the race for 1,144 of 2,286 delegates needed to win the Republican nomination for president. CBS News has estimated that Romney has just shy of 500 delegates, while Santorum has more than 200.

Santorum suggested that none of the candidates would be able to get that "magic number" and the nominating convention in Tampa in August would be the ultimate decider.

"The convention will nominate a conservative," Santorum said, "they will not nominate the establishment moderate candidate from Massachusetts," referring to Romney, who served as the Bay state's governor from 2003 to 2007.

The former Pennsylvania senator, who is known for his strongly held social conservative beliefs, said he is the best messenger for Republicans.

"When we nominate moderates, when we nominate Tweedledum versus Tweedledee, we don't win elections. We win elections when there are clear contrasts and bold choices and that is what we are going to do in this election," Santorum said.

"And that is why we believe that ultimately we will be the nominee," he said.