The New York Times has more on the denials:
They included Stephen Hadley, the national security adviser; Marc Grossman, the former undersecretary of state; Douglas Feith, the former undersecretary of defense for policy; and Eric Edelman, the former deputy national security adviser to Vice President Dick Cheney, who has succeeded Mr. Feith at the Pentagon.
In addition, a person knowledgeable about the investigation being conducted by the special counsel in the case, Patrick J. Fitzgerald, said Mr. Cheney had not been Mr. Woodward's source. A spokesman for Mr. Cheney has said that the vice president would have no comment on a continuing investigation.
....Others who issued denials on Thursday included Carl P. Ford, the former head of the State Department's intelligence bureau; Alan Foley, the former head of the C.I.A.'s weapons and arms control center; and David R. Shedd, chief of staff and associate director of national intelligence who is the former senior director for national security matters on the staff of the National Security Council.
Those who have declined to comment include Robert Joseph, the undersecretary of state for arms control, who was previously a senior director on the N.S.C. staff. Aides to Mr. Rumsfeld; Mr. Armitage; and Paul D. Wolfowitz, former deputy secretary of defense, now head of the World Bank, have not replied to requests to comment.
Richard Armitage is a possibility. The Times reports:
Among other officials with whom Mr. Woodward is known to have interviewed for his previous books are Mr. Cheney; Ms. Rice; former Secretary of State Colin L. Powell; George J. Tenet, former director of central intelligence; and Mr. Armitage.
Washington Post Editor Leonard Downie said on CNN Wednesday that the source was one who had been interviewed many times for Woodward's 2004 book. Armitage reportedly is out of the country and has not replied to inquiries.
Kevin Drum has a handy new guide to those claiming not to be the source. Scrappleface has some comic relief on the topic.
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Original Post 11/17
The White House is adding to its list of officials who deny being Robert Woodward's source for the leak of information about Valerie Plame Wilson. It says Stephen Hadley is not the source:
A White House official said on Thursday that national security adviser Stephen Hadley was not Woodward's source on Plame. According to current and former administration officials and lawyers, neither was: President George W. Bush himself, top political adviser Karl Rove, Libby, White House chief of staff Andrew Card, counselor Dan Bartlett, former Secretary of State Colin Powell, former CIA director George Tenet, and former deputy CIA director John McLaughlin.
Many people are speculating it is Dick Cheney. Jane of Firedgoglake seems like she may be leaning that way. I don't think so. But the list is narrowing. Those who seem most likely to me are all included in this paragraph from the Sunday Herald (Oct. 30, 2005), written before Woodward's revelation:
All The President's Men has a resonance when you follow the links Libby has with other part of Bush's influential regime. Libby's deputy, John Hannah, one of Cheney's leading Middle East experts, had close ties to John Bolton, a former under-secretary of state for arms control; David Wurmser, a former Bolton aide, later joined Cheney's office. Robert Joseph was another hawk within the Bush administration who was a former director for nonproliferation on the National Security Council.
Bolton is now in New York as ambassador to the UN, and Joseph has a new role as under-secretary of state where his executive assistant is Frederick Fleitz, a former CIA officer, formerly John Bolton's chief of staff. Among those quizzed in relation to the leak of Plame's name and CIA role include Hannah and Joseph.
The answer may not be in Woodward's book, Plan of Attack. According to a April 29, 2004 article in The Independent, White House Braced for Latest Assault by Hardback, (available on Lexis.com)
This [Woodward's] volume involved interviews with 75 sources, only two of which - Mr Bush himself and Defence Secretary Donald Rumsfeld - are named.
I'll still go with David Wurmser, John Hannah or Fred Fleitz.