NEW ORLEANS - Republican Sen. John McCain wasted no time last night in launching his first general-election broadside against Sen. Barack Obama, casting the Democrat as an out-of-touch liberal offering a false promise of change.

In a prime-time speech designed to upstage Obama on the night he claimed the Democratic nomination, the Arizona senator began what top aides and other Republicans promise will be an aggressive effort to claim the mantles of reform, experience and mainstream values. Obama, he said, is an "impressive man," but one with a thin record.

"For all his fine words and all his promise, he has never taken the hard but right course of risking his own interests for yours, of standing against the partisan rancor on his side to stand up for our country," McCain said less than two hours before Obama spoke in the same St. Paul, Minn., arena where McCain will claim the Republican nomination in September.

McCain praised New York Sen. Hillary Rodham Clinton, who in the Democratic primary race won over many rural and working-class voters whom McCain hopes to capture in the Nov. 4 election.

"As the father of three daughters, I owe her a debt for inspiring millions of women to believe there is no opportunity in this great country beyond their reach," he said.

Two McCain aides said his speech was the beginning of a "great debate" on the direction of the country. It will be followed quickly 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.

Confronting what his aides expect to be Obama's principal attack against him, McCain explicitly rejected the idea that he represents President Bush's third term.

"Why does Sen. Obama believe it's so important to repeat that idea over and over again?" McCain asked. "Because he knows it's very difficult to get Americans to believe something they know is false."

As evidence of his independence, McCain highlighted his breaks with Bush on Iraq, energy and climate change.

McCain spoke in Kenner, a suburb of New Orleans hit hard by Hurricane Katrina and a place that McCain's campaign said exemplified the government dysfunction that he has vowed to fix.

Obama, in his own speech, honored McCain's service but derided the Republican's claim to stand for change.

A McCain-Obama matchup means voters will have a stark choice in November between two men who both assert they will be the agents of upheaval in Washington. One is a military hero whom Americans have known for decades as a cantankerous lawmaker. The other is a community organizer from the South Side of Chicago who first drew the national spotlight with a soaring speech at the 2004 Democratic National Convention.

McCain crossed the nominating finish line long before Obama but has struggled to take advantage of the extra time. He has spent the last two months unveiling campaign themes and taking swipes at Obama. But his campaign has also been dogged by questions about his age (71) and health, his wife's tax returns, and his connection to controversial pastors and lobbyists.

Some Republican observers have expressed concern about how slowly McCain has moved to match Obama's organizational prowess. He finished the primary season with a skeletal staff, and campaign offices are just now opening in dozens of states.

After watching from the sidelines as Clinton sparred with Obama, top McCain advisers say that the Republican nominee faces the likelihood of a revitalized rival who will quickly seek to unify his party and to tap into the energy among Democratic activists and donors.

McCain advisers concede that the battle for the White House will play out in a political environment that is terrible for Republicans: Gas and food prices are high, economic anxiety runs deep, Bush is pushing an unpopular war, and 80 percent of Americans think the country is on the wrong track.

But those advisers say the Democratic battle has exposed serious weaknesses for Obama, especially among blue-collar voters, and provided a road map for questioning his lack of experience and judgment during the general election.