"The federal investigation into Congressional corruption is approaching a crucial deadline and potential dead end. Feb. 15 is the last day on the job for United States Attorney Carol Lam of San Diego, the inquiry's dedicated prosecutor, who is being purged by the Bush administration.

Her investigation led to the imprisonment of former Representative Randy Cunningham, the California Republican who took millions of dollars in bribes in exchange for delivering lucrative government contracts. But just as Ms. Lam was digging into other possible wrongdoing, the White House decided to force her from office without explanation.

Ms. Lam has been investigating the dealings of Brent Wilkes, a private contractor and deep-pocketed political contributor who was designated co-conspirator No. 1 in the Cunningham case. Mr. Wilkes developed other cozy relationships. Among other avenues, the inquiry has been looking into rich government contracts secured by corporations and lobbyists with ties to Representative Jerry Lewis — the former appropriations chairman — and his staff. The Wall Street Journal is reporting that Mr. Wilkes could be indicted before Ms. Lam leaves office. The question now is whether her successor, as yet unnamed, will pursue the inquiry with the same dedication or will quietly smother it.

The outlook isn't promising. The administration is defenestrating at least six other U.S. attorneys. Yet Attorney General Alberto Gonzales is refusing to provide Congress with details on these unmerited dismissals. He insists that there's no attempt to quash fresh Republican scandals and says only the "very best" will be named as replacements.

We are skeptical, especially since the White House's reported choice to replace Little Rock's federal attorney is a Republican operative close to Karl Rove. Congress must demand a clear explanation from Mr. Gonzales and the White House on why these prosecutors are being ousted. It must search out every shady aspect of this clearly politically motivated purge — with a particular eye on Feb. 15."

(Times editorial)