Arizona voters head to the polls on Tuesday to choose party nominees in races that could help determine who controls the US House of Representatives and whether Republicans can flip one of the country’s most competitive Democratic governorships.

Once considered reliably Republican, Arizona has swung between the two parties in recent election cycles. Democrat Joe Biden narrowly won the state in 2020, while Donald Trump reclaimed it in the 2024 presidential election.

The biggest contest is the Republican primary for governor, where four candidates are competing to challenge Democratic Governor Katie Hobbs in November. The results will also set up key congressional races in one of the country’s most closely watched battleground states.

Here’s what to know.

When will polls open and close?

Polls will open at 6am (13:00 GMT) and most will close at 7pm (02:00 GMT on Wednesday). Anyone in line by 7pm may vote.

Who can vote?

Registered Democrats and Republicans can vote only in their own party’s primary, while independent voters can choose whether to vote in either the Democratic or Republican contest.

There are about 4.3m registered voters in Arizona, including roughly 1.5m Republicans, 1.2m Democrats and 1.5m independents or voters not affiliated with either major party.

What races are on the ballot?

Arizona voters will choose party nominees for governor, congressional seats, state offices, including secretary of state, attorney general, treasurer and state superintendent of public instruction, and all 30 seats in the state Senate and all 60 seats in the state House of Representatives.

Who is running for governor?

One of the most anticipated races is the Republican primary for governor, where four candidates are competing to challenge Democratic Governor Katie Hobbs in November. Hobbs, who is running for her second term, is one of only two Democratic governors seeking re-election this year in states Trump carried in 2024.

While four Republicans are on the ballot, the race has largely become a showdown between Andy Biggs and David Schweikert, two longtime congressmen who represent competing visions for the future of Arizona’s Republican Party.

Biggs, a former chair of the conservative House Freedom Caucus, is closely aligned with Trump and has built his campaign around the president’s agenda. He was among the Republicans who sought to block Congress from certifying Biden’s 2020 election victory and has long been associated with the party’s most conservative wing. Trump endorsed Biggs after previously backing another Republican candidate who later dropped out of the race.

Schweikert has also supported many of Trump’s priorities in Congress, but has cast himself as a more pragmatic conservative. Representing one of Arizona’s most competitive congressional districts, he argues Republicans have lost ground in the state by nominating candidates seen by voters as too extreme.

What are the congressional races to watch?

The primary will also decide who will compete for Arizona’s open 1st Congressional District, a seat left open after Representative David Schweikert decided to run for governor. Covering Scottsdale and northeastern Phoenix, it is expected to be one of the state’s most competitive races in November and could play a role in deciding which party controls the House.

Republicans are choosing between state Representative Joseph Chaplik, former NFL kicker and sportscaster Jay Feely, who has Trump’s endorsement, and technology executive John Trobough.

On the Democratic side, doctor and former state Representative Amish Shah, who narrowly lost to Schweikert in 2024, is competing against former news anchor Marlene Galan-Woods. The registered Republican until 2018 is the widow of former Arizona Attorney General Grant Woods, a prominent Republican who later became a vocal Trump critic.

She is being backed by the national party, which backed Shah in 2024. Publisher Rick McCartney and entrepreneur Jonathan Treble are also on the ballot. Another closely watched House race is in Arizona’s 6th Congressional District, where Republican Representative Juan Ciscomani is seeking a third term against Democrat JoAnna Mendoza, a Marine Corps veteran. Both are unopposed in Tuesday’s primaries and will face each other in November in what’s expected to be one of the Democrats’ best opportunities to flip a Republican-held seat as they try to regain control of the House.

How are Israel and Gaza shaping the Arizona primaries?

The Democratic Party’s growing divisions over Israel’s war in Gaza are becoming apparent in some of Arizona’s congressional primaries, where candidates have clashed over US support for Israel and the direction of the party’s foreign policy. Two races in particular illustrate those tensions.

In Arizona’s 4th Congressional District, which is considered reliably blue, Representative Greg Stanton faces a primary challenge from progressive candidate Kai Newkirk. He has made US support for Israel a central issue in his campaign, arguing that Stanton has been too supportive.

Stanton, a staunch supporter of Israel who has been endorsed by AIPAC, recently voted against a proposal to restrict US military aid to Israel. According to Track AIPAC, an advocacy group that monitors pro-Israel political spending, Stanton has received about $322,000 in donations linked to AIPAC and other pro-Israel groups.

In the neighbouring 3rd Congressional District, Representative Yassamin Ansari has dramatically changed her position on Israel since first running for Congress, reflecting the changing dynamics within the broader Democratic Party.

Ansari received support from Democratic Majority for Israel in her closely fought 2024 primary, but has since become a sharp critic of Israel’s war in Gaza and said she will no longer accept backing from the group or AIPAC.

When will the results be announced?

Polls close at 7pm on Tuesday (02:00 GMT on Wednesday) across most of Arizona, although no results can be released until 8pm local time (03:00 GMT on Wednesday). Because Arizona conducts most voting by mail or through early voting, counties typically report a large share of ballots shortly after polls close.

More than 755,000 ballots had already been cast before election day.

Most races are expected to become clearer during the first few hours of counting, although close contests could take longer if additional mail ballots need to be processed.