He did not mention that Clinton supports a similar plan.
Obama also said he soon will campaign in Michigan and Florida, two battleground states whose Democratic primaries were essentially nullified by party disputes, angering many voters. He is scheduled to campaign Tuesday in Missouri, marking the first such visit to a state where the primary is over and McCain awaits him in the fall.
Saying he still has not secured the nomination, Obama nonetheless entertained several questions about the likely outlines of a contest against McCain. As he campaigned in Oregon, whose primary is May 20, Obama picked up four superdelegate endorsements, erasing Clinton's once-substantial lead among the party leaders who will determine the nominee.
Many party leaders feel it is only a matter of time before the former first lady must concede defeat. But Clinton forged ahead Saturday, holding a fundraiser in New York.
"Let's keep going, stay with me, this is a great adventure and we're going to make history," she told the crowd.
Speaking with reporters in Bend, Ore., Obama brushed aside suggestions that the fall campaign may be largely about his race, liberalism or patriotism.
"In a contest between myself and John McCain," he said, "there is going to be a very clear choice on policy that I don't think is going to have to do with ideology and who theoretically is more liberal or who's more conservative. I think it is going to have to do with who has a plan to provide relief to people when it comes to their gas prices, who has a real plan to make sure that everybody has health insurance, who's got a real plan to deal with college affordability."
"So rather than an abstract set of questions about, 'Is he too liberal, is he too conservative, how do voters handle an African American, et cetera,' I think this is going to be a very concrete contest around very specific plans for how we improve the lives of Americans and our vision for the future," he said.
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.
Appearing with her daughter, Chelsea, Clinton took questions from the audience after a short speech that touched on issues like equal pay for women and balancing work outside the home with family responsibilities. She barely mentioned Obama, only noting their differences on health care and the gas tax.
She said it would be "exciting to have the first mother in the White House."
"Part of what that would mean is that we would have someone who has lived the experiences that many of us share," she said.
Clinton has struggled to raise money in recent weeks, and was set back further this week when she squeaked by with a narrow win in Indiana while Obama won handily in North Carolina. Aides also disclosed that Clinton had lent her campaign $6.4 million since mid-April, and said she had not ruled out doing so again. The recent loans come after a separate $5 million loan in February.
Clinton is favored to win Tuesday's primary in West Virginia, and on Saturday she implored her audience to stick with her.