The president was on his way. Space shuttle Endeavour's astronauts were riding out to the launch pad in a van. And a wounded Rep. Gabrielle Giffords had flown in from her Houston rehab hospital to watch her husband blast off Friday on the historic, next-to-last shuttle mission.
Then it all came to a sudden stop.
Without warning, a faulty heater part forced NASA to scrub the launch and slam the brakes on the space agency's biggest event in years, a flight made more fascinating to many by the plight of Giffords and her husband, Mark Kelly, the mission commander.
Endeavour's flight was delayed until at least Monday.
Travel plans for the Arizona congresswoman, who is still recovering from a gunshot wound to the head from an assassination attempt in January, are still up in the air, said her spokesman, C.J. Karamargin. He said she is waiting until Sunday when NASA should know more about a possible launch date.
Obama and his family came to Cape Canaveral anyway, and he and his family met with Giffords for about 10 minutes. Karamargin said only that Giffords was pleased to meet with them.
The congresswoman's husband greeted Obama in a corridor, saying: "I bet you were hoping to see a rocket launch today."
Obama replied: "We were hoping to see you."
The two men shook hands and embraced.
The president told Endeavour's six astronauts he is still hoping to get back to Florida for a shuttle launch.
As many as 700,000 tailgaters and other spectators had been expected to pour into the seaside area for the liftoff, one of the biggest launch-day crowds in decades. It would have been the first time in NASA history that a president and his family witnessed a launch.
Giffords' Houston doctors declined to say whether a prolonged stay away from her rehab center would cause problems.
Engineers aren't certain what part on the heating system -- needed for launch and landing -- needs to be replaced. To fix the heater, technicians will have to crawl into the engine compartment. If it is a simple fix, NASA could make another launch attempt as early as Monday, Tuesday or Wednesday, but if not, the flight could be delayed to May 8 or later, said launch director Mike Leinbach.
If NASA tries on Monday, the president can't make it, Kennedy Space Center Director Robert Cabana said.
After Endeavour, there is only one more shuttle flight -- by Atlantis -- before NASA ends the program and the orbiters become museum pieces.
Later, at Miami Dade College's commencement in Miami, Obama promised graduates he'll keep working to help undocumented immigrants who study in the United States become American citizens.
The president's renewed endorsement of the DREAM Act that's become a rallying cry for Hispanic and other students around the country drew enthusiastic applause from more than 3,000 graduates.