According to a CBS News poll published on Thursday, only 35% of Americans thought Bush was doing a good job, while 57% disapproved. The survey was conducted after a five-count indictment of Vice-President Dick Cheney's top aide last week.
Bush's job approval rating was down from 37% in a previous CBS poll in October.
I Lewis "Scooter" Libby, Cheney's former chief of staff, faces one count of obstruction of justice, two of perjury and two of making false statements in a federal probe into who leaked the identity of CIA agent Valerie Plame.
Libby pleaded not guilty to all the charges on Thursday.
The CBS poll compared Bush's job approval rating with some other presidents at about the same point in their second term.
In November 1997, in the first year of his second presidential term, 57% of Americans approved of Bill Clinton. The job approval rating of Ronald Reagan in November 1985 was 65%.
A Gallup poll in November 1957 found 58% approval for Dwight Eisenhower.
By contrast, President Richard Nixon's job approval rating was only 27% in November 1973 after the Watergate scandal became public.
The latest CBS poll brought slightly better news for Bush on Iraq.
Fifty-percent of those surveyed believed that US troops should withdraw from Iraq, compared with 59% in October. And 43% said the troops should stay as long it takes, up from 36% last month.
The poll was conducted among a nationwide sample of 936 adults, interviewed by telephone, and has a margin of error of plus or minus three percentage points.