On Tuesday, Arizona will hold its congressional primaries, locking in the candidates for the state’s much-anticipated Senate race in November but also pitching two President Trump-endorsed Republicans against each other in a congressional primary.

It’s widely expected that the candidates will be Congressman Ruben Gallego for the Democrats and TV news host Kari Lake for the Republicans.

On the Republican side, Sheriff Mark Lamb is contesting Ms. Lake in the GOP Senate primary, though recent polling from Noble Predictive Insights suggests that he is running 25 points behind Ms. Lake.

The Arizona race has also evolved over the past two years since the incumbent, Senator Sinema, left the Democratic Party following years of acting as a holdout, alongside Senator Manchin, preventing Democrats from passing major legislation in the upper chamber.

While it initially appeared that the race might evolve into a three-way competition between a Democrat, a Republican, and Ms. Sinema as an independent, she announced in March that she would not seek re-election. 

With Ms. Sinema out of the race, the Senate race will likely mirror the result of the presidential race, in which Arizona plays a key role as one of some six states expected to decide the election.

For Republicans, it will be their first opportunity to win a Senate seat in Arizona since Senator McCain was elected for his final term in 2016.

For Democrats, it will be their opportunity to fill Ms. Sinema’s seat with Mr. Gallego, a congressman who promises to break with Ms. Sinema’s tradition of obstructing Democrats’ legislation from within their own caucus if elected.

In the polls, it appears that Mr. Gallego will enter the general election season with an advantage over Ms. Lake. A recent survey from the Hill and Nexstar of 800 registered voters in the state found he led Ms. Lake 46 percent to 42 percent.

While the 2022 Arizona Senate election saw Senator Kelly defeat venture capitalist Blake Masters by 5 points, the 2020 special Senate election saw Mr. Kelly win by only about 2 points. The 2020 presidential race was even closer, with President Biden carrying the state by just more than 10,000 votes.

Further complicating matters is that Ms. Lake ran for statewide office just two years ago, losing by less than a point to Governor Hobbs, though Ms. Lake often claims to be the current “lawful governor” of the state.

The Cook Political Report’s Jessica Taylor, in her analysis of the race, notes that Ms. Lake’s candidacy appears to have advantaged Democrats in the state, as she remains a divisive figure following her 2022 loss.

“Although there are other re-run candidates on the map this cycle, none bring as much obvious baggage as Lake,” Ms. Taylor wrote.

Vice President Harris is also reportedly considering Mr. Kelly as a potential running mate, which would likely affect other races in the state. Aside from the Senate campaign, the state is also holding primaries in its nine congressional districts, the most notable being Arizona’s Eighth.

In the district, Trump has endorsed two of the Republicans running — the state’s failed 2022 Senate nominee, Blake Masters, as well as a former prosecutor, Abe Hamadeh.

“Blake Masters is a very successful businessman, and an incredibly strong supporter of our Movement to Make America Great Again,” Trump said in a social media post over the weekend. “Likewise, Abe Hamadeh, a Veteran, former prosecutor, and fearless fighter for Election Integrity, has been with me all the way.”

Both candidates have touted Trump’s endorsement, though it’s not clear how the unusual double endorsement will play out in a party where the former president’s endorsement often plays a kingmaking role in primaries. 

Mr. Masters has noted that he also enjoys the endorsement of Trump’s vice presidential nominee, Senator Vance, though it’s not clear how much weight the endorsement carries, especially with Mr. Vance turning out to be a historically unpopular running mate at this stage of the race.

Whoever wins the primary, however, is likely to go on to win the general election for the seat. In 2022, Democrats didn’t contest the seat, which encompasses a swath of Phoenix’s wealthy suburbs, which have supported Republicans in every presidential election since 2004.