The retirement of Rep. Gabrielle Giffords brought an outpouring of warm wishes from colleagues of the popular congresswoman -- and launched a scramble for an upcoming special election to determine whether Democrats will be able to hold the Arizona seat.

By law, the Arizona governor must call a special election within five months, setting up a possible spring primary and summer election for the 8th District seat that has Republican leanings -- for now. Come November, when the seat would again be contested, newly drawn district lines give it a more Democratic tilt.

Republicans have faced a formidable challenge because of Giffords' popularity, but the Tuscon-area seat is a competitive one.

Giffords, 41, is serving her third term, having earned plaudits for her congeniality and her middle-of-the-road approach to lawmaking -- smart politics for the district that stretches from urban Tucson to the Mexican border. During 2010, Giffords parted ways with the Democratic majority 40% of the time on votes that split the parties, according to Congressional Quarterly.

"Gabby Giffords embodies the very best of what public service should be," President Obama said in a statement. "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."

Obama said he was, "confident that we haven’t seen the last of this extraordinary American."

Rep. Nancy Pelosi (D-San Francisco) called Giffords "a true bright star -- a dynamic and creative public servant. Gabby's message of bipartisanship and civility is one that all in Washington and the nation should honor and emulate."

"She will be missed," said House Speaker John A. Boehner (R-Ohio). "I salute Congresswoman Giffords for her service, and for the courage and perseverance she has shown in the face of tragedy."

Giffords announced Sunday in a YouTube video and Twitter message that she was stepping down after three terms in office to focus on her recovery. She suffered a serious brain injury after being shot in the head a year ago when a gunman opened fire at a "Congress on the Corner" event, killing six and wounding 14.
    The congresswoman said she planned to attend Tuesday's State of the Union address in Washington -- an event that will carry her indelible influence. Last year, after the shooting, lawmakers began a tradition of sitting with one another across party lines as a gesture of civility in what has continued to be a highly partisan atmosphere.

"Gabrielle is proving once again that she is a true public servant -- putting the needs of her constituents ahead of her own," said Rep. Steve Israel of New York, chairman of the Democratic campaign arm. “We look forward to working with a Democratic candidate who fits this district and shares those values that Gabrielle holds dear to carry on her work."
   
Arizona Gov. Jan Brewer, a Republican, said in a statement that she will call for special primary and general elections to be held when Giffords' seat is officially declared vacant.

lmascaro@tribune.com

Ashley Powers contributed to this report.