It has been nearly a year since the United States attorneys scandal broke, and much has changed. Many people at the center of the scandal have fled Washington, and new laws and rules have been put in place making it harder to use prosecutors’ offices to win elections. Much, however, remains to be done, starting with a full investigation into the misconduct that may have occurred  something the American people have been denied.

The primary responsibility for giving the public the final answers about what happened, and assurances that it will not happen again, lies with Attorney General Michael Mukasey, House Speaker Nancy Pelosi and Senate Majority Leader Harry Reid.

Over the course of the year, considerable evidence emerged that the Bush administration did what seemed unthinkable: it used federal prosecutors, who are supposed to be scrupulously nonpartisan, to help the Republican Party win elections. As many as nine United States attorneys were fired, apparently because they brought cases against powerful Republicans or refused to bring cases that would hurt Democrats.

When the scandal broke, important players either refused to testify before Congress  like Harriet Miers, a former White House counsel, and Karl Rove, the presidential adviser  or professed ignorance. Then these officials began to slink away. The list of people connected to the scandal who resigned their jobs includes Ms. Miers; Mr. Rove; Kyle Sampson, the chief of staff to then-Attorney General Alberto Gonzales; Monica Goodling, the Justice Department’s White House liaison; and Mr. Gonzales himself.