Six candidates have filed their petitions with enough signatures to be placed on the primary ballot for the April 17 special election in Arizona Congressional District 8. Petition signatures are subject to challenge by interested parties until 5 p.m. Friday.

Republicans on the ballot are state Sen. Frank Antenori, 2010 CD8 candidate Jesse Kelly, retired Air Force Col. Martha McSally and sports broadcaster Dave Sitton.

The Democrat is Ron Barber, who was district office director for Gabrielle Giffords before she resigned last month to continue her recovery from the Jan. 8, 2011 shooting in which both she and Barber were wounded. Six people were killed and 11 others were wounded in the shooting.

The Green Party candidate is Charlie Manolakis, who described himself to the Arizona Daily Star as a community activist.

The primary election will produce the candidates for the June 12 general election. The winner will complete Giffords' term, which expires in January 2013.

Several of the Republican candidates have said they plan to run in the fall for a full term in what will be a redrawn Congressional District 2.

There's still time for challenges of each person's candidacy, but Arizona Secretary of State Ken Bennett says the clock is ticking. Listen to a story about that process, plus whether a crowded Republican primary is an asset or a crutch in the race:

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Your Vote 2012: The AZPM Election Center