Top advisers to Republican presidential candidate John McCain spent much of Tuesday with their feet in their mouths.

Their comments to reporters left openings for Democratic rival Barack Obama’s campaign to exploit throughout the day.

Holtz-Eakin told reporters at a campaign stop in Florida that McCain’s seat on the Senate Commerce Committee was responsible for the invention of one of the most-used devices in Washington.

“If John McCain hadn’t said that ‘the fundamentals of our economy are strong’ on the day of one of our nation’s worst financial crises, the claim that he invented the BlackBerry would have been the most preposterous thing said all week,” Obama campaign spokesman Bill Burton said in a statement.

The McCain campaign said later that Holtz-Eakin was just making a joke.

“It was a joke by a staffer — people need to lighten up,” said McCain spokesman Tucker Bounds. “John McCain heard about the comment and laughed himself. He isn’t laying claim to inventing anything — much less a BlackBerry. Our policy adviser is better with economics than comedy — clearly.”

Holtz-Eakin, according to reports, held up his BlackBerry as an example of “a miracle that John McCain helped create.”

Holtz-Eakin was explaining how McCain’s position on the committee helped him understand financial markets, using his BlackBerry as visual evidence. McCain has noted his computer illiteracy in several interviews. The GOP presidential candidate has also said he doesn’t use a BlackBerry, although his wife Cindy McCain is often spotted with one.

“Telecommunications of the United States is a premier innovation in the past 15 years, comes right through the Commerce Committee, so you’re looking at the miracle John McCain helped create and that’s what he did,” Holtz-Eakin said, according to reports.

Democrats immediately seized on the comment, comparing it to the famous assertion in the 2000 presidential campaign that former Vice President Al Gore invented the Internet. Gore was widely mocked for the remark, but he didn’t actually make the claim. Instead, he had said he helped lay the framework for the Internet through policies he helped initiate, as pointed out by The Associated Press on Tuesday.

And later in the day, Carly Fiorina, McCain’s Victory 2008 chairwoman and the former head of Hewlett-Packard, said in an interview with a St. Louis radio station that McCain’s running mate, Alaska Gov. Sarah Palin, does not have the experience to be the head of a major corporation.

“Do you think [Sarah Palin] has the experience to run a major company, like Hewlett-Packard?” the host of the “McGraw-Hill Show” on KTRS asked.