WASHINGTON – In a White House known for both defiance and optimism, yesterday’s’s senior staff changes represent a frank acknowledgement of the trouble in which President Bush now finds himself. They are also a signal of how starkly Mr. Bush’s second-term ambitions have shifted after a year of persistent problems at home and abroad.

Longtime Bush confidant Karl Rove – who had hoped to use his position of deputy chief of staff to usher in an expansive conservative agenda – was relieved of his policy portfolio to concentrate on long-term strategy and planning for a November midterm election that looks increasingly bleak for Republicans.

Mr. Rove likely will remain one of the most influential voices in the White House, but his shift in responsibilities suggests that the new White House chief of staff, Joshua Bolten, intends to operate a different White House than his predecessor, Andrew Card Jr., who resigned after more than five years at the helm.

Mr. Bolten’s White House, say former administration officials and Republican strategists, is likely to have clearer lines of authority and less freelancing by powerful officials. They also expect Mr. Bolten to play a more active and influential role in shaping domestic policy than did Mr. Card.

More significantly, they said, unlike Mr. Card, who took as his principal responsibility the management of the president, Mr. Bolten likely will operate more in the mold of chiefs of staffs in previous administrations, who saw their role as managing the entire White House and sought to oversee the entire federal government as well.

Whether the changes will bring fundamental change in a troubled administration is another question. One of Mr. Bolten’s biggest challenges, say administration allies, will be to find ways to open up the Oval Office to new ideas and to the opinions of people who are not long-time Bush confidants.

On that score, many people who know the administration best are privately dubious. Presidents, more than chiefs of staff, determine how White Houses operate, they said, noting that Mr. Bush has shown that he prefers a tight circle of advisers and doesn’t welcome the advice of outsiders. As Mr. Bush put it on Monday, in asserting that he would not fire Defense Secretary Donald Rumsfeld, “I’m the decider and I decide what’s best.”

Mr. Rove’s return to a role that closely mirrors that which he played in Mr. Bush’s first term demonstrates how much this White House has now shifted to survival mode – and how far events have pushed the president from the grand ambitions with which he opened his second term just 15 months ago.

Then, with Mr. Rove as the animating force, the president sought to engineer Republican political dominance by remaking government with such far-reaching initiatives as his plan to remake the Social Security program. Today, Social Security stands as Exhibit A of what went wrong domestically in 2005.

Public disillusionment over Mr. Bush’s policies in Iraq have left the country in a sour mood and Mr. Bush’s presidency at low ebb, threatening the entire Bush-Rove project to create a durable Republican majority. While that goal remains central to the those closest to Mr. Bush, the focus at the White House for the foreseeable future will be trying to revitalize this presidency quickly enough to avoid crippling GOP losses in November that could thrust Mr. Bush into instant lame-duck status.

Realigning the White House staff and bringing in new faces appear central to that effort. This week’s changes include yesterday’s resignation of White House press secretary Scott McClellan and appointment of Joel Kaplan as White House deputy chief of staff for policy, as well as Monday’s announcement that U.S. trade representative and former House member Rob Portman would succeed Mr. Bolten as director of the Office of Management and Budget (OMB).

The domestic policy process has been hampered since Mr. Bolten went to OMB, and one Republican strategist close to White House said the new chief of staff appears bent on trying to prevent Mr. Rove and others from interfering in every aspect of the governing process.

Mr. Rove will retain the “gravitational force” of his Bush relationship and could “overpower” Mr. Bolten in showdowns because he knows the president and the inside game better, this official predicted. But he added that Mr. Bolten believed that the strategy to overhaul Social Security was sloppy and hampered by Mr. Rove becoming too involved in every aspect of the campaign – policy, politics, and communications.

Former administration officials said that Mr. Rove, though known for his ability to juggle many roles, was overwhelmed by the sheer volume of his responsibilities when he was promoted to deputy chief of staff after the 2004 election.

In addition, he was engulfed in the CIA leak case for providing false testimony about his role, and remains under investigation by a special prosecutor.

Messrs. Bolten and Rove forged a congenial working relationship during Bush’s first presidential campaign, when Mr. Rove was chief strategist and Mr. Bolten chief policy adviser. That carried over into the White House during the first term, until Mr. Bolten departed as deputy chief of staff to take over as OMB director. Administration allies say they hope that the new assignments can restore a operating arrangement that they believe worked well.

One former administration official, who asked not to be identified in order to speak freely about his former colleagues, called yesterday’s shift in Mr. Rove’s responsibilities a “huge” development. “This is putting back things where they belong,” he said. “It’s given Josh back policy. Joel (Kaplan) is a total Josh disciple and he is very good in the policy world. It focuses Karl back on politics, which is what he needs to do.”

But former Bush spokesman Ari Fleischer said Mr. Rove’s losing the policy portfolio also is significant because the policy job “is where ideas comes from, where creativity comes from and that is where presidents rise and fall.”

“I think this is another building block in bringing in other voices to reenergize and reinvigorate the West Wing,” said Kenneth Duberstein, White House chief of staff to former President Ronald Reagan, who predicted Mr. Rove will remain one of Mr. Bush’s most trusted aides.

Despite his power, Mr. Rove has not been immune from criticism. Inside the White House, some aides were unhappy that he had sent Mr. McClellan out to say inaccurately that Mr. Rove had no involvement in the CIA leak case. Outside allies feared that Mr. Rove was so invested in the policies had had helped to shape and sell to Mr. Bush that he lost his ability to see where the administration had gotten off track.

Mindful that Mr. Rove’s changed responsibilities might be seen as a demotion, administration officials and allies offered a counterview, arguing that, given his personal relationship with the president, he will continue to exercise wide influence on policy and politics while having new freedom to thing more strategically about the administration.

Other changes are expected at the White House and perhaps in Mr. Bush’s Cabinet. One will be a replacement for Mr. McClellan, another is likely to be a new domestic policy adviser. Criticisms of the legislative affairs and communications operations as well as the national economic council suggest the potential scope of changes. But one of the most important steps came yesterday. As one strategist who has worked closely with the administration put it, “I don’t know how you change the White House without changing Karl’s role.”