Voting begins for July 30 Arizona primary election

• More vote centers will open closer to Election Day.

Zoom in: The primary allows voters to select which candidate should represent their party in the November general election.

What we're watching: There are a handful of uber-competitive primaries this year, including:

• CD 1: Six Democrats are sparring to take on incumbent Republican U.S. Rep. David Schweikert, who's seen as vulnerable in this district that spans parts of north Phoenix and Scottsdale.
• CD 3: Former state lawmaker Raquel Terán and former Phoenix Council Member Yassamin Ansari are the front-runners for this open and safe Democratic seat in south and west Phoenix.
• CD 8: Six Republicans are running for the open seat, including pals-turned-foes Abe Hamadeh and Blake Masters.

How it works: Registered Democrats, Republicans, Green Party and Libertarian voters can participate in their party's primary.

• Voters who are registered as "independent" or "no party declared" can select which ballot they'd like to cast.