“Do we really want someone with this little experience?” Mr. Santorum asked, referring to Mr. Paul, Mr. Cruz and Senator Marco Rubio of Florida, who is also in his first term. “And the only experience they have basically — not Rubio, but Cruz and Paul because I don’t think Rubio is going to go — is bomb throwing? Do we really want somebody who’s a bomb thrower, with no track record of any accomplishments?”

Mr. Paul’s top strategist responded that the party should not take advice from a politician who was soundly defeated in 2006…

Mr. Huckabee, who has a following of Christian conservatives, may present the biggest obstacle to Mr. Santorum, who narrowly won the Iowa caucuses in 2012. But Mr. Santorum said Mr. Huckabee would have considerable vulnerabilities on the right.

“He has to talk about Common Core. I love talking about Common Core,” Mr. Santorum said of the education standards that have become deeply unpopular among conservatives. “He has to talk about immigration and the Dream Act. I love talking about immigration and the Dream Act. He has to talk about taxes; I haven’t voted for a tax increase. I have a 100 percent record on taxes, signed every pledge every year.”