By Adam Brookes
BBC News, Washington
President Bush has nominated an Air Force general, Michael Hayden, to be the next director of the CIA.
Gen Hayden is currently deputy director of national intelligence
The position came vacant at the end of last week, when Porter Goss resigned unexpectedly after less than two years in the role.
President Bush was effusive as he nominated Lieutenant General Michael Hayden to be the top man at the CIA.
"Mike has more than 20 years of experience in the intelligence field.áHe served for six years as director of the National Security Agency, and thus brings vast experience leading a major intelligence agency to his new assignment," he said.
Gen Hayden's experience is beyond question. His whole career has been spent in intelligence - as an air force officer, as a military attache in Bulgaria and as head of the super-secret National Security Agency (NSA).
Most recently he has acted as number two in the Office of the Director of National Intelligence. His role - to effect reform of the intelligence community and how its 15-member agencies interact. He is an espiocrat, par excellence.
But you can read Gen Hayden's resume from start to finish and still know very little about the man. Secrecy renders opaque most of his life and work.
When the general comes to be questioned by the Senate... the picture becomes political, and murky
As he accepted the nomination, the master spy spoke only briefly.
But Michael Hayden is in fact known as an engaging, slightly unconventional character.
And Washington insiders say he has impressed the Bush administration as a man adept at bridging the treacherous bureaucratic waters that lie between the spies, the military and the politicians.
But when the general comes to be questioned by the Senate - as he must if he is to be confirmed as head of the CIA ┐ the picture becomes political, and murky.
When he was at the NSA, Gen Hayden oversaw a highly controversial surveillance programme.
The NSA listened to the international telephone calls of Americans without obtaining the normal permissions from a secret court. There was a scandal.
Gen Hayden faced tough public questions about the programme's legality. He defended himself and the surveillance programme robustly.
If senators choose to grill him about the NSA's domestic surveillance programme, his confirmation hearings could turn bloody.
"The odds still would suggest that Hayden will be confirmed in this position," said Norman Orenstein, of the American Enterprise Institute.
"But to get there, the president is going to have to use a very significant amount of political capital at a time when his capital bank is at its lowest ebb."
Senators from the opposition Democratic Party may smell political advantage in opposing the president's candidate, and in publicly revisiting the NSA surveillance.
The president was full of praise for Gen Hayden
But they may also feel that opposing Gen Hayden makes them look weak or obstructionist on national security - a traditional point of vulnerability for the Democrats.
Perhaps the greater threat to Gen Hayden comes from the fact some Republicans have already expressed publicly doubts over his candidacy - not because of the surveillance programme, but because he is a serving officer.
They are concerned that the military should not lead a civilian agency.
Republican Senator Saxby Chambliss said Hayden's military background would be a "major problem".
The background to these concerns is complex. The Pentagon, say intelligence community sources, has over the last few years expanded its intelligence gathering, particularly in the field of human intelligence, or HUMINT.
HUMINT - the actual business of running agents - is traditionally the work of the CIA.
But Pentagon officials have, we're told, sought to expand the remit of Special Operations Command and the Defense Intelligence Agency to include more HUMINT operations.
These officials feel a need for faster, more relevant operational intelligence for America's 'war on terrorism'.
The Pentagon's expansion has led to unease in other areas of the intelligence community.
And, say intelligence sources, maintaining a working equilibrium between the various agencies has been difficult for John Negroponte, the Director of National Intelligence and his deputy, Michael Hayden.
And if the general is confirmed to the CIA, his problems could be just beginning.
The Washington whisper is that morale at the agency is very low.
The failure to stop 911; the flawed intelligence in Iraq; these have left the CIA the butt of jokes - especially in the military.
One admiral recently told me: "If I'm looking for knowledge, I don't look to the CIA."