Rep. Gabrielle Giffords may be released from ICU as soon as this week, ABC News has learned.
The fluid accumulation in her brain that concerned doctors over the weekend has already begun to subside.
Meanwhile, at Tuesday's State of the Union address, members of both political parties were wearing black and white ribbons in a show of solidarity with Giffords and the people of Tucson. In a special gesture, her friends in Congress left one seat unfilled.
"There is going to be a chair left empty to symbolize what we all know will be a triumphant return to the House of Representatives when she comes back to us full strength," said Giffords' friend and colleague, Rep. Debbie Wasserman Schultz, D-Fla.
In Houston, Giffords' husband, NASA Commander Mark Kelly, watched tonight's State of the Union Address from his wife's bedside at the hospital. While he keeps watch over her care, the clock is ticking on a critical decision. Kelly has said he will decide within two weeks whether he will command the space shuttle Endeavor's final mission in April.
"Obviously, Mark has trained with this crew for over a year, and so he is the ideal person," NASA Chief Astronaut Peggy Whitson said.
Over the weekend, doctors inserted a small drain in Giffords' skull to remove the brain fluid that had delayed her transfer out of ICU. Experts say it is not uncommon for someone suffering a traumatic brain injury to have such fluid accumulation, caused when the brain bleeds or swells.
"Pressure built up perhaps too quickly for the brain to accommodate," said Dr. Jonathan Fellus, who specializes in brain injury at the Kessler Institute for Rehabilitation in New Jersey. Fellus said that when left untreated, fluid can be deadly for brain injury patients.
Giffords' doctors have expressed confidence that she has passed the most critical period for complications and say that the fluid is not keeping Giffords from receiving three hours of physical therapy a day.
Giffords' trauma surgeon, Dr. John Holcomb, said in recent days that the fluid buildup, which doesn't appear to be infected, was down a little on Saturday and that Giffords was a little more alert and responsive.
Giffords was brought by a specially equipped private plane from Tucson to Houston's Hobby Airport last Friday, and immediately was transported to the Texas Medical Center's intensive care unit by medical helicopter. She will eventually be treated at nearby TIRR Memorial Hermann.
Kelly, Doctors Share Details of Gabrielle Giffords' Progress
Before departing for Houston Friday morning, Giffords left the Tucson, Ariz., hospital where she had been treated since suffering a gunshot to her head in an attack over two weeks ago. She was the last shooting victim to leave the hospital.
Along her roughly 10-mile route to the Air Force base, crowds of supporters stood on the curb, cheering and waving flags and signs as her motorcade passed by. Giffords' ambulance was escorted by a squadron of military veterans on motorcycles.
"We could hear applause in the ambulance with Gabby, and she responded very well to that, smiling and even tearing a little bit," said Dr. Randall Friese, one of the doctors who treated Giffords in Tucson. "It was very emotional and very special."
At a press conference in Houston late Friday afternoon, Giffords' medical team said that the trip went flawlessly and that while she has a long road ahead, she has great potential for rehabilitation.
Giffords' husband, Kelly, who lives in Houston, said last Thursday that she soon would be "back at work" and predicted she would be walking around in a couple of weeks.
"I'm extremely hopeful that Gabby will make a full recovery," he said. "She is a fighter like nobody else I know."
In other signs of progress, Giffords was taken outside Thursday for the first time since the attack so she could get some sunlight. She stood up Wednesday for the first time with assistance and looked out of a hospital window.
Giffords already has been able to scroll through an iPad, one of many steps described by her doctors as "fantastic achievements forward."
The Associated Press contributed to this report.