(CBS News) - A top campaign adviser to President Obama said the long Republican primary has "weakened" that party's candidates for a match-up against Mr. Obama in the fall.
Robert Gibbs, the president's former press secretary and current campaign strategist, said on CBS News' "Face the Nation" that the negative ads and campaign trail rhetoric has damaged whoever the potential nominee is.
"I know at what these candidates have been saying, tearing each other apart with negative ads, it is a process that in many ways has torn each of them down, and I think has weakened them for a fall election," Gibbs told host Bob Schieffer.
He said the campaign has become "corrosive" for both front-runners Mitt Romney and Rick Santorum. "I think it's become destructive," Gibbs said.
Still, he offered that "it's a fascinating process to watch."
Nearly half of the states have voted in this Republican nominating season, and no candidate is close to achieving the necessary 1,144 delegates necessary to clinch the nomination. Mitt Romney is in the lead with 428 delegates, followed by Rick Santorum with 179 delegates, according to estimates by CBS News.
, Gibbs disagreed. He said the economy is going to the main issue in the election, and that it won't be a referendum on the president, but will be "a choice" between the president's ideas and those of the Republicans.
"We are going to have a choice in this election of whether we are going to continue positive job growth, or whether we are going to go back to the policies of cutting taxes for the wealthy and ignoring the middle class," Gibbs told Schieffer.
As for the Republican nominating process, the candidates are gearing up for several nominating contests Tuesday, including the Southern states of Mississippi and Alabama.
Gibbs, an Alabama native, offered some advice for Romney, who has been telling Southern supporters that he likes cheesy grits and biscuits.
"I wouldn't normally give advice to Republicans, particularly Mitt Romney, but as a Southerner I would tell him that kind of stuff doesn't really go over well in the Deep South," Gibbs said.