Mr. Siegelman’s lawyer, Doug Jones, said the investigation of the former governor was very limited until it turned around “180 degrees” in late 2004, after Washington officials told local prosecutors “to go back and look at the case, review the case top to bottom.” That is consistent with the account of Dana Jill Simpson, a Republican lawyer who says she was on a phone call in which Republican operatives said Karl Rove was involved in the prosecution.

In his introductory remarks, Representative Robert Scott, Democrat of Virginia, said that Mr. Minor’s prosecution appeared to have been political. He said that a Republican contributor who is the brother-in-law of a Republican senator was “not even investigated, let alone indicted” for activities similar to Mr. Minor’s.

Committee members said they have learned of other prosecutions that may have been political and listed several defendants by name. Donald Shields, the University of Missouri professor, testified that the Justice Department prosecuted 5.6 local Democratic officials for every Republican. The odds of that occurring by chance, he found, is less than 1 in 10,000.

Republicans on the committee refused to take the allegations seriously — even though this sort of politicization should offend anyone who cares about the justice system. They called the claims “ridiculous,” and asked the witnesses if they had specific evidence that United States attorneys talked to the president or to other top officials about a plan to target Democrats.

That sounds good, but the best evidence about what occurred lies with the current and former members of the Bush administration — and Mr. Rove and Harriet Miers have pleaded executive privilege and defied Congressional subpoenas. They should testify about what they know, and the Justice Department should hand over documents the committee requested months ago.