Tucson, Arizona (CNN) -- Former Democratic Congresswoman Gabrielle Giffords made a rare appearance before a cheering crowd of supporters at a "Get out the vote" concert in downtown Tucson.
Giffords was joined by her husband, Mark Kelly, at the Saturday event for a special election race for the seat from which she resigned.
The standing-room only crowd gathered at a theater cheered as she walked on stage with her husband, who spoke on her behalf.
"It was incredibly hard for her to resign," Kelly said as Giffords smiled and held hands with her former aide Ron Barber. "And the person she knew could represent this district like she did is standing to my left."
After her husband's speech that drew loud cheers, Giffords said, "Thank you very much."
Giffords was with Barber, who was wounded during the January 2011 assassination attempt that nearly took her life. Now he's running for her seat.
The race to fill her seat has become a nail-biter in a district where Republicans have a 6% advantage in registered voters.
"A lot of volunteers, including myself were working today in 100 degree heat," said Jeff Rogers, chairman of the Pima County Democratic Party.
They went door-to-door, reminding voters of the special election Tuesday.
"We're seeing an awful lot of interest for a special election in the middle of summer," he said.
Neither campaign is releasing any polling data that suggest any lead would be within the margin of error.
In 2010, a year dominated by tea party sentiment, Giffords won re-election by a few thousand votes. She beat Republican Jesse Kelly, who is hoping to win the seat this time around.
"The next 72 hours, what we put into it, we'll get out. It's a razor-thin margin," Kelly, a former marine, told supporters at a Republican volunteer phone bank. "You think last time was close, 4,000 votes? They say this one will be in the hundreds. We gotta work the phones."
Both campaigns centered around jobs and the economy, with the Republican candidate taking a national approach. Kelly has made defeating President Barack Obama part of his message.
"He's gonna win this race for us because this nation is tired of his job killing agenda and they [voters] know that I will go to Washington and fight him," he said.
Barber, a moderate Democrat, says he supports the president, but he's crafted a local message of helping the middle class in southern Arizona.
"Middle class Americans feel they're being squeezed by stagnant wages, underemployment and foreclosures," Barber said. "We need to send someone to Congress who is listening to the people and that's what I've been doing."
The race has attracted interest and money from outside the district.
Super Pacs are at work on both sides, and the Republican National Congressional Committee as well as the Democratic Congressional Campaign Committee have ran ads here.
Whoever wins the seat Tuesday will hold it for only six months and will start running for re-election almost immediately.
That's because come Fall, district lines in the state will move slightly and will become more amenable to Democrats, though still competitive.
Winning the special election matters, says Kate Kinski, who teaches government and communications at the University of Arizona.
"Democrats don't want to lose and Republicans want to ensure that come Fall, and they won't quite have those margins that they have now, that they still have an opportunity to try to win this (new) district," she said.
Giffords resigned her seat as she was undergoing rehabilitation after the attack that left left six people dead last year. Her resignation prompted the special election to choose a successor for the remainder of her term in Arizona's 8th District.