WASHINGTON — For months, Rep. Gabrielle Giffords, who was shot in the head in an assassination attempt a year ago, signaled that returning to Congress, something she desperately longed to do, was in the realm of the possible.
She listened pensively as her friend, Sen. Kirsten Gillibrand of New York, briefed her on the conflict in Libya. She cast a vote to raise the nation's debt ceiling. Her congressional aides continued to churn out news releases outlining her positions and hold community meetings, and she and her husband gave an interview to 60 Minutes in which she demonstrated her improving ability to speak.
But Giffords, a moderate Democrat from Arizona whose remarkable comeback stirred the nation, decided in recent days that she could not continue her recovery and still serve as a member of Congress. On Sunday, she announced that she would step down.
Giffords' decision shook up the race for her seat representing Arizona's 8th District. She barely fought off her Republican challenger in 2010 but was expected to be a shoo-in for re-election if she had decided to run this year.
"She could have definitely done it," Gillibrand said. "But I think she made a realization, if she really wanted to focus on the recovery, she shouldn't."
In a moving video released online Sunday afternoon, Giffords, in a halting voice, explained to her constituents: "I don't remember much from that horrible day, but I will never forget the trust you placed in me to be your voice. Thank you for your prayers and for giving me time to recover. I have more work to do on my recovery, so to do what is best for Arizona, I will step down this week."
But Giffords hinted at a potential return to elective office. "I will return, and we will work together for Arizona and this great country," she said.
On Jan. 8, 2011, Giffords, who is in her third term, was one of 19 people shot at a meet-and-greet political event outside a grocery store in her hometown of Tucson. Six people died, including a 9-year-old girl, Christina-Taylor Green, and a federal judge, John M. Roll.
The suspect in the shooting, Jared Loughner, a 22-year-old college dropout, has been charged with numerous federal counts, including the attempted assassination of a member of Congress.
The remainder of Giffords' term will be filled by the winner of a special election, to be held on a date determined by Gov. Jan Brewer, a Republican. In November, the district will be redrawn in a way that further favors Democrats, which may scare away some Republicans.
Democrats, fearing the loss of the seat, had hoped that Giffords' husband, Capt. Mark Kelly, a retired astronaut, would run in her place. Friends of the couple said they thought that was not likely, and Kelly would be more inclined to spend his time helping his wife with her recovery.
While Giffords' ability to understand what people say to her is strong, she does not have the language skills to express her responses. "She can get across how she feels and what her views are," Gillibrand said, but her ability to communicate effectively is hindered "because she can't talk in paragraphs. That is the development she wants to focus on."
According to her office, Giffords will go back to the supermarket parking lot in Tucson where she was shot for a private event, which will include some of the people who were at the meet-and-greet last year.
Giffords, who will officially resign to congressional officials later this week, will also attend President Barack Obama's State of the Union address on Tuesday night in the House chamber.
On Sunday, Obama released a statement that read in part: "Gabby Giffords embodies the very best of what public service should be. She's universally admired for qualities that transcend party or ideology — a dedication to fairness, a willingness to listen to different ideas, and a tireless commitment to the work of perfecting our union."
John A. Boehner, a Republican who became House speaker only days before the shooting, said in a statement on Sunday: "I salute Rep. Giffords for her service, and for the courage and perseverance she has shown in the face of tragedy. She will be missed."