Two Senate Democrats called Thursday for the appointment of a special counsel to take over the investigation of the corruption scandal spawned by lobbyist Jack Abramoff.

The switch "would ensure that the investigation and prosecution will proceed without fear or favor and provide the public with full confidence that no one in this country is above the law," Sens. Charles Schumer of New York and Ken Salazar of Colorado wrote Attorney General Alberto Gonzales.

The two Democrats said that so far, the public integrity section of the Justice Department, which is in charge of the probe, has "pursued this case appropriately."

Abramoff pleaded guilty earlier this year to several felony charges, some of them involving his dealings with members of Congress and their aides. His one-time business partner, former congressional aide Michael Scanlon, pleaded guilty last year as part of the same investigation.

Officials have said numerous former congressional aides remain under scrutiny, as does Rep. Bob Ney, R-Ohio, who recently stepped down temporarily as chairman of a House committee.

Politicians of both parties moved quickly to shed campaign donations from Abramoff or his former clients in the wake of the lobbyists' admission of guilt.

The scandal also has thrust congressional reform toward the top of the legislative and political agenda in the opening days of an election-year Congress.

Schumer and Salazar sent their letter several days after Democrats pressed the White House for information on contacts between the president or other top officials and Abramoff. So far, the White House has refused to release any photographs of the president and the lobbyist together.

Asked about the issue at a news conference Thursday, Bush said, "There's thousands of people that come through and get their pictures taken.

"I'm also mindful that we live in a world in which those pictures will be used for pure political purposes," he said, "and they're not relevant to the investigation."

In their letter, Schumer and Salazar cited news reports that said that in addition to the presidential photographs, Abramoff organized at least one meeting with White House aides for his clients.

"These meetings with the president and the White House staff occurred while you were serving as White House counsel," they wrote Gonzales, who became attorney general a year ago. "Given the possible ties between Mr. Abramoff and senior government officials, we believe the appointment of a special counsel is not only justified, but necessary."

Schumer and Salazar wrote that the "highly political context" of the allegations may "lead some to surmise that political influence may compromise the investigation."

They cited allegations that the former acting U.S. attorney for Guam and the Northern Marianas, Frederick Black "was replaced, perhaps improperly, as a result of his investigation of Mr. Abramoff." Abramoff had clients in the islands.