This one could be big.

The McCain campaign today found itself on the defense after its own economic adviser, Phil Gramm, was quoted as saying that America was in the midst of a “mental recession,” and that we have “sort of become a nation of whiners.”

Ouch.

To make matters worse, the McCain campaign initially stood by the comments, and the Obama camp pounced.

“He said we’re in a mental recession,” said Sen. Obama before a crowd of 2,000 in Fairfax, VA. “I guess what he meant was it’s a figment of our imagination, these high gas prices.” But, Obama said, “It’s not just a figment of your imagination, it’s not all in your heads, when people are struggling with the rising cost of everything from gas to groceries…this economic downturn is not in your head.”

Double ouch.

The McCain camp later denounced Gramm’s remarks, and Talking Points Memo’s Josh Marshall is reporting that the Arizona senator’s staff is so concerned about the remark’s ramifications that it has apparently been pushing a YouTube video in which McCain “bashes” Gramm. Gramm, for his part, has defended his comments, saying that “I’m not going to retract any of it. Every word I said was true.”

Will the comments hurt McCain in the long run? The potential is definitely there. But perhaps more importantly, if it’s true that, as the McCain camp says, “Phil Gramm’s comments are not representative of John McCain’s views,” then why is the man serving as McCain’s economic adviser?