The shooting was not the first time the congresswoman has had brushes with violence. Following the health care overhaul vote this year, her district office was vandalized.
"The rhetoric has gotten incredibly heated," she told MSNBC in March. "Not just the calls, the emails, the slurs. Things have really gotten spun up."
She also specifically called out a "targets" website created by former Alaska Gov. Sarah Palin for the 2010 midterm elections that featured a crosshair over hers and other districts. Republicans campaigned heavily against Ms. Giffords, a moderate Democrat in a Republican-leaning district, this year.
"We can't' stand for this, we do really need to realize that the rhetoric and firing people up, and you know things for example we're on Sarah Palin's targeted list, the thing is the way she has it depicted has the crosshairs of a gunsight over our district," she told MSNBC.
Rep. Giffords earned a reputation as a strong fundraiser and campaigner who was deeply engaged in Arizona's bitter immigration debate.
A member of the fiscally conservative Blue Dog Coalition, she won a tough reelection battle last fall against a Republican, Jesse Kelly, who was championed by many tea-party groups. She won the race by fewer than 4,000 votes.
Tea Party Nation, the group started by Tennessee lawyer Judson Phillips, put out a statement to its supporters decrying the shooting. "Congressman Giffords was a liberal, but that does not matter now. No one should be the victim of violence because of their political beliefs."
The statement went on to say that "no matter what the shooter's motivations where, the left is going to blame this on the Tea Party Movement."
The 8th District shares a 100-mile-long border with Mexico.
Ms. Giffords' district is overall politically moderate, represented for years by an openly gay, moderate Republican, Jim Kolbe, then by Ms. Giffords. But the GOP in southeastern Arizona is deeply divided. A moderate Republican hand-picked by Mr. Kolbe to succeed him after he retired in 2006 was beaten badly by Randy Graf, a staunch conservative who ran a strong, anti-immigration platform. He was in turn beaten badly by Ms. Giffords.
The pattern repeated itself in 2010. While Arizona Democrats were swamped in November, Ms. Giffords survived in large part because Republican primary voters picked the most conservative candidate to challenge her.
The district includes part of Tucson, but also large stretches of ranch lands stretching to the Mexico border, where anti-illegal-immigration sentiment runs strong. During the runup to the November election, the other Tucson representative, liberal Democrat Raul Grijalva, had his office vandalized.
Ms. Giffords' family owns tire stories in the area.