Washington ? Ethics class is in session at the White House.

From presidential advisers to low-ranking aides, workers began attending mandatory lectures on ethical behavior and the handling of classified documents Tuesday after the recent indictment of a high-level official in the CIA leak case.

More than 3,000 employees from agencies and offices under the Executive Office of the President are required to attend the hourlong briefings over the next two weeks. The sessions this week are reserved for staff with security clearances.

Andy Card, the president’s chief of staff, and Harriet Miers, the White House counsel, attended the first lecture, given by Richard Painter, the White House attorney who handles ethics issues. Otherwise, people are to attend by alphabetical order.

The briefings were an outgrowth of the indictment of I. Lewis Libby, Vice President Dick Cheney’s former chief of staff, on charges of perjury, obstruction of justice and lying to FBI agents in the leaking of the identity of CIA operative Valerie Plame, wife of Bush administration critic Joseph Wilson. Libby’s indictment says he got information about Plame’s identity in June 2003 from Cheney, the State Department and the CIA, then spread it to reporters.

The leak case has been costly for Bush. His approval ratings have dropped to a record low for his presidency and there has been a sharp decline in the number of people who say they view him as honest and trustworthy. Just 36 percent now say Bush has lived up to his campaign pledge to restore integrity to the White House, according to a poll released Tuesday by the Pew Research Center for the People & the Press.

“There’s a dark cloud hanging over the White House. It’s really a storm cloud,” Senate Minority Leader Harry Reid, D-Nev., said at a news conference. He said Cheney, in particular, was involved in manipulating intelligence to sell the war in Iraq, was favoring big oil companies over consumers and was behind the leaking of classified information to discredit White House critics.

Reid and other Senate Democratic leaders sent Bush a letter asking him to pledge not to pardon Libby or anyone else should they be found guilty in the leak case. Libby has pleaded not guilty, and special prosecutor Patrick Fitzgerald is said to be still considering whether Karl Rove, Bush’s top political adviser, illegally misled investigators.