Sen. Lindsey GrahamLindsey Olin GrahamAlabama election has GOP racing against the clock Graham on Moore: 'We are about to give away a seat' key to Trump's agenda Tax plans show Congress putting donors over voters MORE (R-S.C.), who declined to endorse in the South Carolina Republican primary, said Saturday’s result happened because Newt Gingrich convinced voters he could beat President Obama in the November election.

Graham said on CBS’s Face the Nation that Gingrich won the primary more than any other candidate lost it.

“The debate Monday night in Myrtle Beach was probably the best explanation of conservatism in a bold fashion coming from Newt I’ve heard in decades,” Graham said.

Graham helped lead an attempted Republican coup against Gingrich in the House in 1997 to oust the then-speaker. But during the 2012 presidential race Graham has said that Gingrich “matured” since his time as speaker, a line he repeated Sunday.

While Graham said he was still not endorsing Gingrich, he praised his ideas on dealing with illegal immigration, a prickly topic for Republicans.

“Newt Gingrich has changed a lot in a positive way,” Graham said. “Newt’s putting on the table real solutions in a way today that he wouldn’t have done in 1994.”

Appearing with Graham, former Gov. Haley Barbour (R-Miss.), said Gingrich was able to change voters’ minds over the last few months that he was in fact able to beat Obama.

“Newt was really helped by the fact that a lot of people who maybe didn't think he could win three months ago have come to that conclusion,” said Barbour. “Of course, if we would have said three months ago that Mitt Romney was going to win the South Carolina primary, we'd all have laughed at that, too.”

Barbour, who had considered a presidential run in 2011 but passed, said that a long primary season could be healthy in many ways. “As it gets personal,” he added, “that’s negative.”