In the latest blow to a struggling White House, a key ally in the evangelical Christian movement claimed he had been told that Ms Miers only emerged as the leading candidate after several better known conservative jurists withdrew their names, rather than submit to a bruising Senate confirmation battle.

James Dobson, head of the hugely influential Focus On The Family ministry and often described as the "kingmaker of the religious right", said that he had been so informed in a conversation with Karl Rove, Mr Bush's deputy chief of staff. This undermines the President's claim that Ms Miers had been his first choice. Mr Dobson's remarks, in a transcript of his regular radio broadcast, are the latest in a string of developments that have left White House aides scrambling to save the nomination.

The assumption had been that when it came to the crunch, conservative Republicans would go along with Mr Bush's choice. But no one is sure any longer.

Many leading conservative commentators have already poured scorn on a nomination they damn as cronyism. Ridicule has been added to scorn by the release of correspondence in Texas between the state's then governor and his personal lawyer and close aide. "Dear Governor GWB, You are the best governor ever," Ms Miers wrote in a 1997 birthday card to Mr Bush.

Ultimately, Ms Miers' fate will be decided by the Senate. But even there, 27 of the 55 Republicans have expressed reservations about her. The New York Times said staffers to six of the 10 Republicans on the Senate Judiciary Committee that will conduct the confirmation hearings opposed her.