When U.S. President George W. Bush stepped to the podium at NASA headquarters here Jan. 19, 2004, to call for returning humans to the Moon by 2020, cynics could be forgiven for giving the Vision for Space Exploration little chance of succeeding.

Many watching the president's speech that day also had been watching 15 years earlier when the first President Bush delivered a speech on the steps of the National Air and Space Museum calling for sending humans back to the Moon in preparation for eventual missions to Mars.

The Space Exploration Initiative, or SEI, never progressed beyond viewgraphs, its growth stunted by an unsupportive Congress, infighting between the White House and NASA, and a hastily calculated price tag that gave the nation sticker shock. By its third anniversary, the SEI was little more than an inadequately funded Office for Exploration run by then-associate administrator Mike Griffin.

Today Griffin runs all of NASA, wielding a $16 billion budget more than a fifth of which is dedicated to building a space shuttle replacement capable of launching astronauts on trips to the Moon.

For Griffin, there is no comparison between what has been accomplished under the Vision for Space Exploration in the first three years and how far SEI got in the same amount of time.

"The Vision for Space Exploration was enacted as the law of the land," Griffin said in a recent interview, referring to the NASA Authorization Act of 2005 endorsing building new vehicles to replace the space shuttle and carry astronauts to the Moon by 2020.

Congress also has shown its support with money, providing $9 billion for exploration since Bush rolled out the vision. While a substantial amount of that funding initially went towards now-defunct legacy projects rolled into the exploration program--notably the proposed multibillion dollar Prometheus space nuclear systems initiative--NASA has received sufficient budget to go well beyond the viewgraph stage. Scott Horowitz, the former NASA astronaut hired away from ATK Thiokol in late 2005 to run the U.S. space agency's $3.4-billion-a-year-and-growing Exploration Systems Mission Directorate, said the vision has progressed in its first three years from a statement of goals and objectives to a bona fide program that has signed contracts and started building hardware.

"[W]e are already cutting metal and testing components for Ares I and Orion," Horowitz said. "By year four, we will have all major elements under contract to provide the new capabilities to replace the space shuttle after it retires in 2010."

Griffin echoed those comments in a recent interview.

"We have vehicles in procurement right now and others yet to come," Griffin said. "We're grappling with the real world of program management in the Washington environment, the SEI was shut down frankly when President Clinton came to power. We're in an entirely different world."

That world, however, is far from perfect. NASA has not been given the budget increases the White House initially promised, forcing the agency to make unpopular cuts to science and aeronautics to keep its human spaceflight programs adequately funded. And a decision by the new Democratic Congress to fund most federal agencies this year at last year's levels has left NASA's exploration planners struggling with a $500 million shortfall that Griffin recently announced would delay the introduction of the Orion Crew Exploration Vehicle and its Ares I rocket to 2015.

While NASA still hopes to shoot for the Moon by 2020, agency officials readily concede the next four years or so are all about completing the International Space Station, retiring the shuttle, and building and testing Ares and Orion. Work on the heavy-lift rocket, lunar lander and other hardware needed to send astronauts to the Moon is not due to really get started before the shuttle is done flying. Even the series of robotic precursor missions Bush called for in his landmark 2004 address now appears likely to be scaled back to a lone Lunar Reconnaissance Orbiter and a piggy-back payload NASA added to the mission because it had room on the rocket.

No less a hardcore human space exploration proponent that Griffin recently acknowledged that -- at least for now -- the vision is primarily a space shuttle replacement effort.

"Many folks have said, 'I'm not worried about the Moon right now.' I would say to them, 'I'm not worried about the Moon right now either.' I'm worried about replacing the shuttle," Griffin told the Senate Commerce space and aeronautics subcommittee during a Feb. 28 NASA budget hearing.

Of the more than $16 billion NASA plans to spend between now and 2010 on exploration systems, roughly 80 percent is designated Orion and Ares, with the rest budgeted for lunar robotics programs, space station-based research, and other advanced technology development efforts.

By 2011, the first year NASA expects to be out from under the $3 billion to $4 billion a year it spends on shuttle, exploration systems is expected to consume nearly half of NASA's total budget, with upwards of 90 percent of exploration funding going toward completing Ares and Orion and getting started on the Ares 5 heavy-lift rocket and other Moon-bound hardware.

Whether NASA gets to hold on to the money freed up by retiring the shuttle and use it to shift its space exploration plans into a higher gear remains to be seen.

John Logsdon, a NASA advisor and George Washington University space policy expert, said whoever wins the White House in 2008 will have no choice but to see Orion through to completion if he or she wants the United States to have its own means of launching humans into space. Continuing to fly the shuttle will not be an option, he said, because--as NASA's human spaceflight chief William Gerstenmaier put it recently--the agency is already nearly "past the point of no return" on retiring the shuttle.

But the next president will get to decide, Logsdon said, whether to stop with fielding a new capsule capable of going to the space station or push on with the necessary investment to send humans to the Moon. That decision, he said, will happen in 2010 when the White House and NASA prepare their first post-shuttle budget.

"That's the budget in which the decision on how to use the resources freed up by ending shuttle flights will be made," Logsdon said. "That's when we make the decision [about whether we] are we going to take Ares V, the lunar lander and Earth departure stage into development or not ... We could just decide to go on with the utilization of the station and fly Orion [there] for a decade or more."

How much progress NASA is able to make on Orion and Ares by the time there is a new president in the White House depends on much more near-term political decisions, starting with this year's budget.

Griffin recently warned that giving NASA anything less than its full request for 2008 would inflict "grave and lasting damage to the program."

To NASA's advantage, the agency has some key lawmakers out looking for more money for the agency, including Sens. Barbara Mikulski (D-Md.), the chairwoman of the Senate Appropriations subcommittee that drafts NASA's budget; Bill Nelson (D-Fla.), the chairman of the Senate Commerce space and aeronautics subcommittee, and his Republican counterpart Kay Bailey Hutchison of Texas.

In the House of Representatives, however, there are fewer strong NASA supporters in key positions.

House Science and Technology Committee Chairman Bart Gordon (D-Tenn.) said in a recent interview that he supports the Moon-Mars initiative, but does not think his views are widely shared among his House colleagues. "There's not much of an understanding of it," he said, a political reality he blames on the president's failure to promote the vision the way he does other policy priorities. "So it's not a matter so much of not supporting it, but supporting other NASA interests more. That's the dilemma we have."