Confident that he has built a near-impregnable lead, his campaign aides said Wednesday that Obama would begin shifting his focus toward the general election.
Obama still plans to campaign in states that remain on the primary calendar -- he is to appear in Oregon over the weekend -- but he may also start showing up in states that are considered important in the November contest: Ohio, Florida and Pennsylvania. (All three have held their Democratic primaries.)
With Clinton's hopes of capturing the Democratic nomination dimming, Obama needs to prepare for the prospect of a general election matchup with the presumptive Republican nominee, Sen. John McCain of Arizona, aides said.
"Everyone is eager to get on with this," said David Axelrod, the Obama campaign's lead strategist.
"We've got to multi-task here . . . Sen. McCain has basically run free for some time now," Axelrod added.
Clinton's campaign cast Obama's strategy as a show of hubris. Clinton has given no signal she is dropping out of the race after Tuesday's split results, when she lost decisively in North Carolina and won narrowly in Indiana.
Showing she still believes she can win, the New York senator hastily arranged a campaign stop Wednesday in West Virginia, which will hold its primary Tuesday. "We've seen the perils of saying 'mission accomplished' too early," said Phil Singer, a Clinton campaign spokesman.
The phrase "mission accomplished" was famously displayed on an aircraft carrier in 2003, when President Bush came aboard and declared that major combat operations in Iraq had ended.
Obama's pivot reflects a hardening belief in his camp that there are few realistic scenarios under which Clinton can capture the nomination. Because neither Obama nor Clinton ran away with the Democratic race, party insiders known as superdelegates are likely to be the ones to decide who will win.
Even when Obama was embarrassed by the furor over explosive remarks made by his former pastor, the Rev. Jeremiah A. Wright Jr., superdelegates were still breaking for the Illinois senator at a healthy clip, campaign aides said. So they are confident Clinton won't reverse the trend.
What Obama is planning has a dual motive, some Democratic strategists say. Apart from pressuring McCain, Obama may want to rebut the argument that he has faltered in large swing states. By campaigning in those states, he can demonstrate to nervous superdelegates that he will compete aggressively against McCain.
"There's a certain cleverness in the strategy," said Peter Fenn, a Democratic strategist not aligned with either campaign, who says Obama is saying, " 'I can prove to everybody I can handle John McCain' -- which is of course about the only argument that Hillary Clinton has left in this."
Obama already devotes considerable time to McCain at his rallies. Before the Indiana and North Carolina primaries, there were moments when Clinton seemed an afterthought in contrast to the time Obama spent criticizing McCain.
As Obama begins acting like the de facto nominee, Clinton is giving no quarter. Her campaign said she wouldn't settle for anything less than the top job.
Harold M. Ickes, a top advisor to Clinton, said in an interview that the second spot on the ticket had no allure. He cited her election-night party Tuesday, when Clinton said she was moving "full speed on to the White House."
Ickes: "She meant the Oval Office, not the office down the hall."