By Jazmine Woodberry
TUCSON, Arizona (Reuters) - A Republican challenger maintained a slight lead on Wednesday over U.S. Representative Ron Barber, a former aide to Democrat Gabrielle Giffords who was wounded alongside the congresswoman in a deadly shooting last year.
With thousands of ballots still to be counted, Martha McSally, a retired Air Force colonel and former combat pilot, was ahead of Barber by a slender 1,312 votes, the Arizona Secretary of State's office reported.
About 40,000 early ballots and another 40,000 provisional ballots have yet to be counted, the Pima County Recorder's Office said. There were 220,812 votes cast.
Barber, 66, had been considered the front-runner in the contest for the newly created 2nd District. He won a special election in June to serve out the term of Giffords, who suffered a head wound when a gunman opened fire with a semiautomatic pistol at an event at which she was speaking in Tucson. Six people were killed and 13 were wounded.
"The race remains too close to call. Thousands of ballots have yet to be counted, the exact number of which are to be determined," Barber aide Jessica Floyd said in a statement.
Floyd said there were reports of "numerous problems" with voting in Pima County, although she did not specify what they were.
"We will continue to monitor this process and hope to ensure that every person who voted in Southern Arizona has their voice heard," she said.
McSally, 46, was the first U.S. woman pilot to fly in combat, completing two tours in the Middle East. She said she had no indication from election officials when the final tally might be released, but felt optimistic.
"This is not a traditional ending to our general election, but I guess there's nothing traditional about my life so far, so why start now?" she told reporters at a news conference.
"We're not surprised that we're in this position ...We've been telling people all along this is going to be a very close race," she added.
McSally campaigned on a platform of cutting federal regulations and reducing debt and taxes. She also pledged to tighten security on the porous U.S.-Mexico border.
Barber was boosted by an endorsement from Giffords, whose popularity and political stature soared as she battled through a difficult recovery.
Giffords, who moved back to her native Arizona earlier this year after undergoing rehabilitation in Houston, turned out with Barber to vote early at a Tucson polling station on Monday.
(Writing by Tim Gaynor; Additional reporting by David Schwartz; Editing by Cynthia Johnston)