For months, senators have listened to a parade of well-coached Justice Department witnesses claiming to know nothing about how nine prosecutors were chosen for firing. This week, it was the turn of Bradley Schlozman, a former federal attorney in Missouri, to be uninformative and not credible. It is time for Senator Patrick Leahy, the chairman of the Judiciary Committee, to deliver subpoenas that have been approved for Karl Rove, former White House counsel Harriet Miers and their top aides, and to make them testify in public and under oath.

Mr. Schlozman was appointed United States attorney in Missouri while the state was in the midst of a hard-fought Senate race. In his brief stint, he pushed a lawsuit, which was thrown out by a federal judge, that could have led to thousands of Democratic-leaning voters being wrongly purged from the rolls. Just days before the election, he indicted voter registration workers from the liberal group Acorn on fraud charges. Republicans quickly made the indictments an issue in the Senate race.

Mr. Schlozman said it did not occur to him that the indictments could affect the campaign. That is hard to believe since the Justice Department’s guidelines tell prosecutors not to bring vote fraud investigations right before an election, so as not to affect the outcome. He also claimed, laughably, that he did not know that Acorn was a liberal-leaning group.

Mr. Schlozman fits neatly into the larger picture. Prosecutors who refused to use their offices to help Republicans win elections, like John McKay in Washington State, and David Iglesias in New Mexico, were fired. Prosecutors who used their offices to help Republicans did well.