Democrat Ron Barber, Gabrielle Giffords' former district director, won the special election Tuesday to succeed his former boss in Arizona's 8th District, holding the open House seat for his party and earning a leg up in the race for a full term.

Barber defeated Republican Jesse Kelly, a Marine veteran and Giffords' 2010 challenger, capturing 52 percent of the vote in the Tucson-area district.

The district leans Republican but remains highly competitive territory, prompting national interest from outside groups as well as party strategists in Washington. Republicans attempted to capitalize on the low approval numbers of both President Barack Obama and his health care law, tying Barber to each, while Barber cast Kelly as an opponent of Social Security.

"Ron Barber's strong campaign made this a referendum on the Republican plans to drastically cut Medicare and privatize Social Security, while giving massive tax breaks to millionaires, Big Oil and corporations that ship jobs overseas," said Steve Israel, chairman of the Democratic Congressional Campaign Committee. "The Republican plan lost."

Israel said Democrats plan to focus their campaigns on similar themes this election year.

Barber is expected to be sworn in soon to represent the open seat, which Giffords vacated in January amid her continued recovery from a January 2011 shooting attack at a town hall event. Barber also sustained injuries in that attack.

But this isn't the last time Barber and Kelly will be competing.

While Barber is now set to serve out the remainder of Giffords' current term, voters will still need to choose a representative for the next session of Congress beginning in January 2013. Due to redistricting, most of the current 8th District has been incorporated into the newly drawn and renumbered 2nd District, for which Barber, Kelly and additional candidates are already running. The primary for that race is Aug. 28.

Barber's win Tuesday offers him an advantage heading into the fight for a full term.

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