Former U.S. Sen. Phil Gramm, a top adviser to John McCain, resigned Friday from McCain's presidential campaign after he was criticized recently for describing America as a "nation of whiners" and as suffering from a "mental recession."

"It is clear to me that Democrats want to attack me rather than debate Senator McCain on important economic issues facing the county," Gramm, McCain's campaign co-chairman, said in a written statement. "That kind of distraction hurts not only Senator McCain's ability to present concrete programs to deal with the country's problems, it hurts the country."

He added that though he is leaving the campaign, he is joining the "growing number of rank-and-file McCain supporters."

Gramm, a Texan who now is the No. 2 at the Swiss bank UBS, told The Washington Times last week the United States has benefited from globalization but most Americans are misguided by constant reports that the economy is at its worst in 30 years.

"We have sort of become a nation of whiners," he said. "You just hear this constant whining, complaining about a loss of competitiveness, America in 'decline' despite a major export boom that is the primary reason that growth continues in the economy."

McCain distanced himself from the remarks, and Gramm later told a cable network that he was calling the country's leaders whiners, not the American people as a whole, but stood by his "mental recession" remark.

The fallout provided fodder for McCain's Democratic rival, Barack Obama.

"The question for John McCain isn't whether Phil Gramm will continue as chairman of his campaign, but whether he will continue to keep the economic plan that Gramm authored and that represents a continuation of the polices that have failed American families for the last eight years," Obama campaign spokesman Hari Sevugan said in a statement after Gramm announced he was leaving his post.