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Arizona Daily Star, Mamta Popat
Martha McSally, candidate for Congressional District 2, makes a speech to supporters during a Republican election night party at the Sheraton Tucson Hotel and Suites, Tuesday, Nov. 4, 2014, in Tucson, Ariz.

PHOENIX — The vote count in Arizona's 2nd Congressional District seat is shaping up as a near mirror of the 2012 race, when the two candidates didn't find out for more than a week who had won the race.

Democratic Rep. Ron Barber and Republican Martha McSally are keeping a close eye on the emerging vote tally in two southern Arizona counties that make up the district as they remain separated by a razor-thin vote margin.

McSally's lead of 363 votes grew to 509 votes Friday night with new votes counted in Republican-leaning Cochise County and Democrat-leaning Pima County.

McSally is taking 60 percent of the vote in Cochise County, and there are fewer than 1,200 provisional ballots to count here. Barber is taking 52 percent of the Pima County vote, and that county has 24,000 outstanding early and provisional ballots still to count.

Barber consultant Rodd McLeod said the trend is the same as in 2012, when election-night counts showed Barber trailing McSally before surging in late ballots to pull out a late victory.

"With more than 20,000 ballots to go, we're confident that Ron Barber will have been re-elected once the counting is all done," McLeod said.

McSally and Barber faced off in a similar battle during the 2012 election. Barber trailed for days, finally taking the lead on the Friday after Election Day. But the race remained too close to call for another week.

Barber had won a special election to replace his former boss, Rep. Gabby Giffords, just months before the November 2012 election. He was with Giffords at a constituent meet-and-greet in Tucson in January 2011 when a mentally ill man, Jared Lee Loughner, opened fire, killing six and wounding 13 others. Giffords was hit in the head and ultimately had to step down from her seat, while Barber was hit in the thigh and cheek.

McSally is a former Air Force pilot who was making her first run for political office. This year, she has emerged as a more polished candidate. With the swing district up for grabs in a Republican-leaning year, her efforts drew massive outside spending from GOP-leaning groups.

Barber also has benefited this year from a large amount of spending by Democratic groups and from Giffords' PAC.