There have been changes at the top in the White House in an apparent effort to turn around President George Bush’s falling popularity ratings. Featuring prominently in the shake-up is Press Secretary Scott McCellan, who has resigned from post. “The White House is going through a period of transition. Change can be helpful. And this is a good time and a good position to help bring about change. I’m ready to move on,” he said.McClellan’s departure is part of an initiative by new White House Chief of Staff Karl Josh Bolten. Karl Rove, Bush’s top policy advisor, is also affected. Officials in the White House say he will give up this role to concentrate on his political duties. It is thought he will focus on the Republicans’ efforts to retain power in Congress in mid-term elections. Rove is still under scrutiny in a prosecutor’s investigation into the leak of a CIA agent’s identity three years ago.