The key southwestern general election battleground state of Arizona holds primaries on Tuesday, which will set the stage for likely competitive autumn showdowns that may determine control of the House and Senate.
The contest grabbing the most national attention is the race to succeed Sen. Kyrsten Sinema, the Democrat-turned-independent who is not seeking a second six-year term in the Senate.
Kari Lake, the front-runner for the Republican Senate nomination, on the eve of the primary teamed up with former President Trump for a tele-rally. Lake is a top surrogate for the former president as he seeks to regain the White House and gave an address two weeks ago at the Republican National Convention in Milwaukee.
SINEMA'S BLOCKBUSTER 2024 ANNOUNCEMENT
Lake, the former TV anchor and major MAGA supporter who never acknowledged her narrow 2022 election defeat for governor, enjoys Trump's backing as she runs for the Senate in a race that is one of a handful that may determine if the GOP wins back the chamber's majority.
WATCH: KARI LAKE OFFERS OLIVE BRANCH TO THESE VOTERS IN ARIZONA
Besides enjoying the Republican presidential nominee's support, Lake also has a major fundraising advantage over her two GOP primary rivals: Pinal County Sheriff Mark Lamb and neuroscientist Elizabeth Reye.
When Sinema announced in March that she wouldn't run for re-election, she was already facing a challenge from Democrat Rep. Ruben Gallego, who launched his Senate campaign last year. Gallego is unopposed in Tuesday's primary for the Democrat nomination.
Democrats control the Senate with a 51-49 majority, but Republicans are looking at a favorable Senate map with Democrats defending 23 of the 34 seats up for grabs. Three of those seats are in red states Trump easily carried in 2020: West Virginia, Montana and Ohio.
Five other seats are in key swing states narrowly carried by President Biden in 2020: Arizona, Michigan, Nevada, Pennsylvania and Wisconsin.
In the race for the House, the GOP holds a fragile majority in the chamber. And in Arizona, Democrats are aiming to unseat two vulnerable Republican incumbents in districts Biden carried four years ago.
In the 1st Congressional District, which includes parts of northeast Phoenix and surrounding suburbs, seven-term GOP incumbent Rep. David Schweikert is the front-runner in a field of primary rivals that includes businessman Robert Backie and former FBI agent and corporate investigator Kim George.
There's a crowded field of Democrats vying for their party's nomination.
In the southeastern part of the state, Republican Rep. Juan Ciscomani is running for a second term in a district that includes much of suburban Tucson.
He's facing off on Tuesday in a GOP primary that includes challenger Kathleen Winn, who came in third in the 2022 nomination race.
If Ciscomani wins the primary as expected, he'll face off in November against Democrat Kisten Engel in a rematch of their extremely close 2022 election showdown.
Meanwhile, in the red-leaning 8th Congressional District, Trump has endorsed both major candidates in the Republican primary, Blake Masters and Abe Hamadeh, who ran unsuccessfully for U.S. Senate and state attorney general in 2022.
