Obama said he realizes he must continue introducing himself to millions of Americans who do not know him well, and acknowledged that some question his patriotism because he no longer wears a lapel flag pin.
He said the test of patriotism "is whether we are true to the ideals and values upon which this country was founded," and willing to fight for them "even when it's politically inconvenient."
Obama said McCain has received "a free pass" while he and Clinton have battled for months.
McCain, he said, "has a straight-talker image, but it's not clear that lately he's been following through on that image. I mean, this gas tax holiday was a pander. He didn't even have a way of paying for it."
The McCain campaign noted that Obama, as an Illinois state senator, once voted for a temporary gas tax suspension. Obama now says he made a mistake.
Obama was asked Saturday if the fall campaign might touch on the 1987 Keating Five scandal, in which the Senate Ethics Committee said McCain used "poor judgment" for allegedly pressing regulators to go easy on the owner of a failed Arizona savings and loan who was also a campaign contributor.
Obama said there is no doubt the Keating Five case is "germane to the presidency."
"I can't quarrel with the American people wanting to know more about that," he said.
Clinton, meanwhile, spent the afternoon in Manhattan raising money for her cash-strapped campaign.
She made her pitch to a crowd of several hundred people, most of them women -appealing to the group that has largely been responsible for keeping her in the race this long. In the primaries to date, Clinton has held a 60 percent to 36 percent edge over Obama among white female voters.

The HTC Droid Eris began selling available alongside the Motorola Droid today in...
The New York City will give 500 tickets for the ceremony on Thursday from 2:00 p.m. to 4:00 p.m. EST.


Online distributor for point of sale equipment, TYSSO and Pegasus.