Polls will open in Pima County and throughout Arizona for the 2012 primary election at 6 a.m. Tuesday and remain open until 7 p.m.

Election officials say that many voters, perhaps a majority of those participating in the primary, have already cast ballots and mailed them in or dropped them off.

At stake are party nominations in numerous races in Southern Arizona, including:

-- U.S. Senate, Republican Party.

-- U.S. House, Districts 1, 2 and 3, Republicans and Democrats.

-- Legislative Districts 2, 3, 4, 9, 10, 11 and 14. Some candidates are unopposed, but candidates in both major parties face opposition in several races.

-- Pima County sheriff, Republican Party.

-- Pima County Board of Supervisors in Districts 1 and 4, Republicans.

Close of polling at 7 p.m. is the deadline for turning in early ballots.

Find where to vote in Pima County here.

Your Vote 2012: The AZPM Election Center