Four Senate Judiciary Committee Democrats on Thursday asked the Justice Department to appoint a special prosecutor to investigate whether Attorney General Alberto R. Gonzales lied under oath to Congress.

Meanwhile, Judiciary Chairman Patrick J. Leahy , D-Vt., subpoenaed White House deputy chief of staff Karl Rove and J. Scott Jennings, a White House political aide, for testimony and documents, setting an Aug. 2 deadline that the White House is likely to ignore.

“If there are any cooler heads at the White House, I urge them to reconsider the course that they have taken because there is a cloud over the White House and a gathering storm,” Leahy said on the Senate floor.

The quartet of senators — Charles E. Schumer of New York, Dianne Feinstein of California, Russ Feingold of Wisconsin and Sheldon Whitehouse of Rhode Island — convinced that Gonzales has repeatedly committed perjury in congressional testimony, most recently during a July 24 appearance before the Judiciary panel — asked Solicitor General Paul D. Clement to name a special counsel from outside the department to investigate.

“His instinct is not to tell the truth, but to dissemble and deceive,” Schumer said.