Law-enforcement sources have said Ashcroft is ready to move on, after four years of intense scrutiny as well as surgery in March to have his gallbladder removed after he was diagnosed with a severe case of pancreatitis.
His aides downplay the significance of his possible departure, noting that the average length of service for an attorney general is about two years.
Ashcroft's predecessor, Janet Reno, served eight years, and was the longest-running attorney general since the Civil War.
But Ashcroft's tenure has also been marked by pitched battles with civil rights groups and members of Congress over his treatment of illegal immigrants after the attacks of Sept. 11. The department's record for prosecuting terrorism suspects has been marred by a number of setbacks, including a Detroit judge's decision in early September to throw out the first jury verdict in a post-Sept. 11 terrorism case, based on evidence of widespread prosecutorial misconduct.
The uncertainty about Ashcroft's future comes as his standing with the administration would seem to be rising, with social conservatives, who drove his nomination four years ago, playing a key role in the president's reelection.
Gonzales, who has indicated privately that he is interested in the job, would be the first Latino to become U.S. attorney general.
PepsiCo's statement on Thompson, who was named the company's senior vice president and general counsel in August, said that he was "proud for the service he has given to the president and the nation, but is excited about the new opportunity he is just beginning with PepsiCo, and is fully engaged and committed to that endeavor."
