Sen. John McCain portrayed himself yesterday as an agent of change with a history of fighting entrenched interests, and not President Bush's clone as Democrats would have voters believe.

Later, Sen. Barack Obama criticized McCain on his Iraq stance, saying he has essentially ignored the economy and other pressing domestic issues. The 46-year-old senator from Illinois is the first African-American ever to win a major political party presidential nomination and lead it into a general election.

He'll face McCain, 71, of Arizona, at a time when Americans are anxious about the economy at home and wars in Iraq and Afghanistan.

Their campaigns are certain to offer very different visions.

Obama opposed the Iraq war from the start. McCain, a heroic former prisoner of war, is the supporter of invading Iraq who pushed for more troops, not fewer, when the long conflict looked increasingly dire.

McCain embraces the Bush administration's economic policies favoring private-sector leadership and low taxes, while Obama favors higher taxes on the wealthy, lower taxes on the middle class and more government intervention in economic affairs.

McCain yesterday described Obama as captive to an unsuccessful liberal ideology.

"I have a few years on my opponent, so I am surprised that a young man has bought in to so many failed ideas," McCain said. "Like others before him, he seems to think government is the answer to every problem, that government should take our resources and make our decisions for us."

McCain delivered his speech on the day Obama clinched the Democratic nomination; many candidates would have let Obama have his moment, figuring they'd get little coverage anyway.

McCain told a crowd of about 600 people at a convention center on the banks of Lake Pontchartrain, in Louisiana, that "no matter who wins this election, the direction of this country is going to change dramatically. But the choice is between the right change and the wrong change."

AD CAMPAIGN TO FOLLOW

Two McCain aides said his speech will be followed by a television ad campaign aimed at reinforcing McCain's core message: that Obama's sweeping rhetoric offers little real promise of changing the political culture in Washington.

Obama, for his part, saluted McCain's life of public service but insisted that they have very different agendas.

"I respect his many accomplishments, even if he chooses to deny mine. My differences with him are not personal; they are with the policies he has proposed in this campaign."

He criticized McCain for standing too often with Bush, supporting economic policies he said have hurt American jobs and paychecks, and for maintaining support for the Iraq war.

"We must be as careful getting out of Iraq as we were careless getting in — but start leaving we must," Obama said.

Much of the general election is likely to be defined by Democrats' attempts to portray McCain as running for "a third Bush term," and McCain's attempts to emphasize his independence.

McCain yesterday enumerated a series of differences with Bush, who suffers one of the worst public approval ratings in modern history.

"I have worked with the president to keep our nation safe," he said. "But he and I have not seen eye-to-eye on many issues. We've disagreed over the conduct of the war in Iraq and the treatment of detainees; over out-of-control government spending and budget gimmicks; over energy policy and climate change; over defense spending that favored defense contractors over the public good."

And he criticized Obama for engaging in intellectual dishonesty by rhetorically tying him to Bush.

"Why does Sen. Obama believe it's so important to repeat that idea over and over again? Because he knows it's very difficult to get Americans to believe something they know is false," McCain said. "So he tries to drum it into your minds by constantly repeating it, rather than debate honestly the very different directions he and I would take the country. But the American people didn't get to know me yesterday, as they are just getting to know Sen. Obama. They know I have a long record of bipartisan problem solving."

Obama heads into the fall campaign with some advantages, notably broad dissatisfaction with Republicans, opposition to the Iraq war and concerns about the economy. Three out of four Americans think the country is on the wrong track, polls show.

OBAMA'S CHALLENGES

Yet Obama also emerges from the nomination battle with challenges made clearer by the campaign.

For one, he lost several battleground states since March 4, including Ohio, Pennsylvania and West Virginia. He struggled to win over rural voters, Roman Catholics, seniors, union members, Hispanics and whites — a broad slice of America that Republicans vowed yesterday to court.

His long fight with Hillary Clinton also called attention to his lack of experience in foreign policy, national security, management and government.

Republicans yesterday vowed to take the fight to Obama, calling him too liberal for the country and dependent on too narrow a coalition to govern.

"The more we can focus the general election on specific issues and not let Obama talk about general things like change and the audacity of hope," said Republican National Committee chairman Mike Duncan, "that gives McCain the opening to put together a center-right coalition, which is a winning coalition most of the time in American politics."

McClatchy-Tribune News Service, the Washington Post and Associated Press contributed to this report.