Ross D. Franklin / AP

Rep. Gabrielle Giffords and Ron Barber celebrate early Tuesday.

Updated at 12:54 a.m. ET: Democrat Ron Barber has won a special House election in southern Arizona to finish the term of former Rep. Gabrielle Giffords, The Associated Press projected.

Giffords, who was critically injured in a Jan. 2011 event in her district, resigned earlier this year.

A former aide to Giffords, Barber, who was also injured in the attack outside a supermarket that left six dead and 12 others injured, faced a challenge from Jesse Kelly, a Republican who narrowly lost to Giffords in the 2010 midterm elections.

The campaign was imbued with emotions that still linger from the attack, which forced Giffords’s retirement – despite remarkable progress toward recovery – earlier this year. But the special election campaign has also assumed a degree of political significance, given each party’s aggressive efforts to win the seat.

Bruising battle
The race evolved into a bruising battle between Kelly and Barber, fueled by hundreds of thousands of dollars of outside spending in the campaign. The district will be redrawn for this fall’s election, slightly in Democrats’ favor. But Giffords first won accolades for her political resiliency in a district that Republicans have won in the previous three presidential elections.

Democrats focused their resources on painting Kelly as an extremist who would seek radical changes to Medicare and Social Security even well beyond what most House Republicans had voted for in Wisconsin Rep. Paul Ryan’s budgets the past two years.

House Majority PAC, a Democratic super PAC, released one particularly effective ad featuring video of Kelly talking about eliminating corporate taxes and calling Social Security and Medicare Ponzi schemes.

Giffords herself made several public appearances in the past week – along with her husband, former astronaut Mark Kelly – pushing for her onetime aide.

A loss for Democrats would have threatened another demoralizing loss, though, on the heels of Republicans Gov. Scott Walker’s survival of a recall campaign last week in Wisconsin.

Both sides will inevitably spin the results of Tuesday’s primary as a harbinger for their chances come November, though the ultimate takeaways from this race might actually be more limited.

Testing ground for attacks
Democrats’ path toward retaking the majority in the House never ran through this seat, which they had controlled since Giffords first won in 2008. Barber will have to stand for re-election in November, and Republicans – including Kelly – vow to contest that race, too. But the district will favor Democrats more slightly, and it’s not clear how inclined that national Republicans will feel to invest heavily in that campaign.

But the race against Kelly provided Democrats in Washington a testing ground for their attacks against Republicans this fall associated with Medicare and Social Security.

Additionally, Republicans gained traction versus Barber by trying to tie him to House Minority Leader Nancy Pelosi and President Obama.

Barber had hedged for a period on whether he would support Pelosi as Democrats’ leader as elected, and he similarly punted on a May question about whether he would even vote for Obama. (Barber later clarified that he intended to vote for the president in November.)

But the fact that a Democratic candidate would feel the need to distance himself from Obama in Arizona raises questions about the viability of the president’s effort to win that state this fall. The Obama campaign has included Arizona in several of its Electoral College roadmaps; the state is rated Lean Republican in NBC News’ battleground map.

The Associated Press contributed to this report.