The Center for American Progress Action Fund, which describes itself as progressive and is headed by former Clinton administration official John Podesta, said Rumsfeld's letter to U.S. President George Bush was dated Nov. 6, and Bush saw it the next day, which was Election Day.
However, Bush didn't make the announcement until a day later, after voters had swung heavily to Democratic candidates.
Asked by reporters in Washington about the decision to delay the announcement, White House Deputy Press Secretary Dana Perino said she hadn't seen the letter but said Bush's action was understandable.
"I know that one of the things that the president wanted to avoid was the appearance of trying to make this a political decision," she said. "And that was very important to him and I think that the American people can appreciate not playing politics with such an important decision."