>> at the height of it, during the house vote, a moment of pure joy arrived. it started with slow applause, and then erupted as house members realized that gabby giffords had come back to cast a vote. something no one thought possible back in january when they didn't know if she would make it through that first night. nancy pelosi called giif i have fords entrance a great moment for our country which, of course, the debate was not. but it's where we begin with nbc's kelly o'donnell.

>> reporter:  at first, the unexpected sound of applause turned heads on the house floor. then the stunned recognition that really was her. congresswoman gabby giffords had come back, steadied by her husband, mark kelly and chief of staff.

>> it was incredible. a moment that we had been hoping for, praying for, thinking about since january 8th.

>> reporter:  a few snapshots had been the only glimpse until now. colleagues could not wait to greet her, touch her. new jersey democrat is still choked up about it.

>> it was heart felt. she smiled, i hugged her and then i raised her hand because she's a champion. when you just think about all that she's been through, how the hell can we complain about our late nights over the last month?

>> reporter:  debbie wasserman schultz was by her side.

>> we knew she would make a triumphant return. we knew her and predicted that it would happen.

>> reporter:  it had been six months, three weeks and four days since those shots were fired in tucson. if i have fords life was nearly taken. giffords life was nearly taken. she returned to take some of that life back. she tweeted, the capitol looks beautiful and i'm honored to be at work tonight. her desk has been empty while her staff keeps going in her place. she had a private meeting with staffers today.

>> she's heading back to houston today to get back to therapy first thing tomorrow morning.

>> reporter:  giffords did not cast the deciding vote needed to pass the debt limit deal. but her vote made a difference. all that bitter fighting seemed to melt in the moment.

>> i don't think she had any sense that it would be as overwhelming and as emotional as it was. i mean, she had members from both parties coming up to her, hugging her, kissing her.

>> reporter:  close friend senator gillibrand had lunch with giffords today.

>> she understands everything. she has opinions on everything. to be able to fully articulate her thoughts the way she did before this awful crime, i think, will be her challenge.

>> reporter:  friends say they expect congresswoman giffords will ultimately decide to run for re-election next year and senator gillibrand said she would help her raise money and campaign. aides say it's too soon for that. for now she's focused solely on her recovery.

>> a moment everybody needed. kelly o'donnell on the hill.