There is yet another United States attorney whose abrupt departure from office is raising questions: Debra Wong Yang of Los Angeles. Ms. Yang was not fired, as eight other prosecutors were, but she resigned under circumstances that raise serious questions, starting with whether she was pushed out to disrupt her investigation of one of the most powerful Republicans in Congress.

If the United States attorney scandal has made one thing clear, it is that the riskiest job in the Bush administration is being a prosecutor investigating a Republican member of Congress. Carol Lam, the United States attorney in San Diego, was fired after she put Randy Cunningham, known as Duke, in prison. Paul Charlton, in Arizona, was dismissed while he was investigating Rick Renzi. Dan Bogden, in Nevada, was fired while he was reportedly investigating Jim Gibbons, a congressman who was elected governor last year.

Ms. Yang was investigating Jerry Lewis, who was chairman of the powerful House Appropriations Committee. Ms. Lam and most of the other purged prosecutors were fired on Dec. 7. Ms. Yang, in a fortuitously timed exit, resigned in mid-October.

Ms. Yang says she left for personal reasons, but there is growing evidence that the White House was intent on removing her. Kyle Sampson, the Justice Department staff member in charge of the firings, told investigators last month in still-secret testimony that Harriet Miers, the White House counsel at the time, had asked him more than once about Ms. Yang. He testified, according to Congressional sources, that as late as mid-September, Ms. Miers wanted to know whether Ms. Yang could be made to resign. Mr. Sampson reportedly recalled that Ms. Miers was focused on just two United States attorneys: Ms. Yang and Bud Cummins, the Arkansas prosecutor who was later fired to make room for Tim Griffin, a Republican political operative and Karl Rove protégé.