COLUMBIA, S.C. — Mitt Romney’s campaign on Wednesday intensified its criticism of Newt Gingrich, seeking to portray the former House Speaker as an unreliable and bombastic leader as he gains momentum here in South Carolina.

Top campaign surrogates, former Missouri Sen. Jim Talent and former New York Rep. Susan Molinari, told reporters that Gingrich ultimately derailed the conservative cause while leading the party in the mid ‘90’s — and contributed to President Clinton’s decisive re-election in 1996.