New Delhi, Aug. 18 -- Voters in Florida, Alaska and Wyoming will head to the polls Tuesday for key state primaries, while California voters will decide a special congressional election. The contests will determine party nominees for several high-profile races and could offer an early indication of the political landscape ahead of the November midterm elections.

With 77 days remaining until the general election, several races stand out because of their competitive fields, open seats, redistricting battles and potential implications for the balance of power in Washington.

Here is a look at what elections are being held Tuesday, the key contests and the candidates involved.

Florida's primary elections are among the most closely watched co...