By James Westhead
BBC News, Washington
As he strode onto the White House lawn, Scott McClellan grinned bravely over one of his last announcements as the public voice of the president - his own resignation.
Mr McClellan's departure comes as support for the president slumps
It is the second high-profile departure in an ongoing shake-up of a White House team that has been largely unchanged in six years.
His voice cracking with emotion, Mr McClellan told the press and the president: "I'm ready to move on... I've given it my all, Sir."
He added: "The White House is going through a phase of transition - a change can be helpful."
The scale of that change became clearer when it emerged that the president's political guru and chief adviser, Karl Rove, was to shed responsibility for domestic policy to concentrate on crafting a winning strategy for the Republican Party in November's mid-term elections.
The moves are part of an effort by the new White House chief of staff, Josh Bolten, who started work last weekend, to try to help Mr Bush rebound from sagging polls and bolster confidence in his leadership.
Mr Bush's job approval ratings have slumped dramatically, partly through growing public disillusion with the Iraq war, but also over sharply rising energy costs.
The latest survey, in the Wall Street Journal, suggests his rating has now slipped eight percentage points since January to a new low of 35%.
The White House has also been battered by a series of domestic political scandals, from a row over port security to its handling of Hurricane Katrina and a criminal investigation into the leaking of a CIA official's identity.
Senior Republicans have accused the president's team of fumbling these explosive problems through poor communication and for months have been calling for change.
"The president is in perilous political shape," says Brooking Institute analyst Thomas Mann. "This administration is looking for anything that might get them out of trouble."
However most experts agree that the changes are more decorative than fundamental.
Another political analyst, and editor of Congressional Quarterly, Chris Lehmann, describes the shake-up as "merely rearranging the furniture at the White House".
He argues: "This is the way an administration creates the illusion of change at minimal cost to itself - it's an old dog doing a not-very-new trick."
The question now is who will succeed Scott McClellan in the notoriously tough press secretary job.
One insider said: "It's like being [Vice-President] Dick Cheney's hunting buddy - you've got to be prepared to take a face-full of birdshot every day."
There have been calls for Mr Rumsfeld's resignation
It is likely the White House has already lined up its replacement to announce in the next few days.
Top candidates include current Treasury spokesman Rob Nicholls, as well as Fox News Radio host Tony Snow, a presidential speechwriter for Mr Bush's father.
One theory is that he would be more effective than Mr McClellan at connecting with Republican voters and stemming the flood of support from Mr Bush's key base.
An even bigger question is whether this is the end of the shake-up.
There has been much speculation about Defence Secretary Donald Rumsfeld, with several recently retired generals calling for his resignation over his handling of the Iraq war.
However Mr Bush has strongly supported Mr Rumsfeld as "doing a fine job", so his departure now would be highly damaging.
The president must be hoping that a change of faces rather than a change of direction will help stem his political problems as he joked: "It's the game of musical chairs, I guess you'd say, that people love to follow."