Martin Sheen knew The West Wing would be axed after the death of castmate John Spencer.
Spencer, who played Chief Of Staff LEO MCGARRY in the White House drama, died in December 2005 of a heart attack, aged 58.
Sheen tells British film magazine Empire, "When John Spencer died, the wind left our sails, the boat stood still and we decided to abandon ship.
"He was such an integral part of the focus and energy and image of the show that it was not possible for it to continue with any real credibility.
"We thought, 'We'll call it quits here.'"