Mr. ObamaÕs triumphs capped a week in which he went undefeated in states across the country, in many cases by big margins, over Senator Hillary Rodham Clinton of New York.

And his strength on Tuesday sliced across nearly every major demographic line, with one element standing out: in Virginia and Maryland, according to surveys of voters leaving the polls, he beat Mrs. Clinton among women.

The sheer consistency of Mr. ObamaÕs victories over the last few days certainly suggests that many Democratic voters have gotten past whatever reservations they might have had about his electability or his qualifications to be president.

Mr. Obama, in his victory speech in Madison, Wis., acted almost as the primaries were behind him, offering a case against the probable Republican nominee, Senator John McCain of Arizona, as he spoke disparagingly of ÒBush-McCain Republicans.Ó It amounted to a preview of what an Obama-McCain race might be like, and it reduced Mrs. Clinton, at least for one night, to the role of bystander.

ÒJohn McCain is an American hero,Ó Mr. Obama said before a huge, cheering crowd. ÒWe honor his service to our nation. But his priorities donÕt address the real problems of the American people, because they are bound to the failed policies of the past.Ó

Mr. McCain picked up the challenge. While not mentioning Mr. Obama by name, he offered an unmistakable put-down of the theme that has become so closely identified with Mr. Obama.

ÒTo encourage a country with only rhetoric rather than sound and proven ideas that trust in the strength and courage of free people is not a promise of hope,Ó he said. ÒIt is a platitude.Ó

To make sure no one had missed the message, Mr. McCain appropriated Mr. ObamaÕs signature line with a sly farewell to his own audience in Alexandria, Va. ÒMy friends,Ó he said. ÒI promise you, I am fired up and ready to go.Ó

Even before his latest victories, Mr. Obama, of Illinois, had whittled away at the advantages amassed last year by Mrs. Clinton.

He now enjoys a big financial advantage. Her big lead in national polls is gone. By most counts, Mr. Obama can now claim more delegates pledged to him. He has won far more states than Mrs. Clinton, although she won some of the big prizes, like California and New Jersey.

For weeks, Mrs. Clinton and Mr. Obama had approached this race the same way: as state-by-state trench warfare, in the belief that the nomination would go to whoever got the most delegates.

But the latest results suggest that the race might be tilting back to a more normal form, where the goal is achieving a series of splashing victories and thus momentum. That has provided Mr. Obama with the opportunity, which he plans to seize in a more full-throated way starting on Wednesday, to argue that voters across a wide cross-section of the country have embraced his candidacy, and that the time has come for the group that could hold the balance of power, those 796 unpledged superdelegates Ñ party leaders and elected officials who have an automatic seat at the national convention Ñ to follow suit.

ÒWe are in a momentum phase of the process now,Ó said Tad Devine, a Democratic consultant.