Voters in three states — Arizona, Florida and Oklahoma — head to the polls Tuesday in some of this year’s latest nominating contests, including a critical Senate race and about half a dozen open-seat primaries.

Arizona hosts the most high-profile race with Republicans choosing their nominee for the open Senate seat being vacated by retiring GOP Sen. Jeff Flake. 

Florida boasts the most numerous primaries Tuesday, with competitive contests in several open seats seen as safe for Republicans as well as primary challenges to at least two Democratic incumbents. Democrats will pick their nominees in a few GOP-held seats they’re targeting this year, although most are mostly a foregone conclusion at this point.

And in an Oklahoma runoff, voters will likely pick a new member of Congress from the safe Republican 1st District.

Arizona Senate race

Most eyes in Grand Canyon State will be on the GOP Senate primary, with three contenders vying to take on Democratic Rep. Kyrsten Sinema in the open-seat race. While Sinema is considered the likely nominee, she does have a primary opponent in lawyer Deedra Abboud.

On the Republican side, GOP Rep. Martha McSally is facing off against former state Sen. Kelli Ward and controversial former Maricopa County Sheriff Joe Arpaio. Recent polling has shown McSally ahead, but the competitive and late primary has raised questions whether the winner can shift quickly to the general election. McSally did start attacking Sinema on the airwaves last week.

Inside Elections with Nathan L. Gonzales rates the general election a Toss-up.

Watch: House Ratings Change in Favor of Democrats

Arizona House targets

Both parties are targeting House seats in Arizona, with Democrats eyeing Tucson-anchored 2nd District seat that McSally is vacating. Hillary Clinton carried the district by 5 points in 2016, and the Democratic Congressional Campaign Committee has thrown its support behind former 1st District Rep. Ann Kirkpatrick’s bid.

But the former congresswoman was unable to clear the Democratic field. Physician and former state Rep. Matt Heinz, the 2016 nominee, has stepped up his attacks on Kirkpatrick for not being from the area originally (Heinz also lives just outside the district), even financing a lawsuit challenging her candidacy. Heinz has also aired negative ads against his opponent’s former positions on gun control, and Kirkpatrick has also hit back on the airwaves. The Democratic nominee will likely face Lea Marquez Peterson, the president of the Tucson Hispanic Chamber of Commerce. Inside Elections rates the 2nd District race Tilts Democratic.

Republicans are also targeting freshman Democrat Tom O’Halleran in the expansive 1st District. O’Halleran is one of a dozen Democrats in districts that President Donald Trump carried in 2016 (He carried the 1st by 1 point). Some Republicans have touted Tiffany Shedd, a lawyer, farmer, and firearms instructor, as an example of an impressive recruit for Republican women, who could see their ranks shrink in the House this November. But Shedd has been outspent by Wendy Rogers, an Air Force veteran who has run unsuccessfully for Congress before, and one national Republican said Rogers is considered the favorite to win.

Rogers is tying herself to Trump, borrowing his “America First” slogan for her campaign website. The primary race has gotten heated between Rogers and state Sen. Steve Smith, with the latter recently calling on Rogers to drop out over attack ads that link the modeling agency he works for to sex trafficking.

Sinema’s Senate run also opens up her Phoenix-area 9th District seat, which Republicans are targeting this cycle. But the GOP faces a tougher climb here in a district Clinton carried by 16 points and in a year when the national environment is expected to favor Democrats. Former Phoenix Mayor Greg Stanton is running unopposed on the Democratic side and is likely to face GOP physician and Navy veteran Steve Ferrara. Inside Elections rates the race Solid Democratic.

Florida’s safe GOP seats

Trump’s endorsement of Rep. Ron DeSantis in a crowded Republican gubernatorial primary has drawn national attention to the Sunshine State, where the president’s influence weighs heavily on races all the way down the ballot. That’s added an extra layer of interest in a year with an unusual number of competitive seats.

There are open-seat races in four districts. Inside Elections rates the races in three of them — the 6th, 15th and 17th — as Solid Republican. Only one, retiring GOP Rep. Ileana Ros-Lehtinen’s 27th District, is likely to flip.

In the 6th District where DeSantis is decamping to run for governor, Republicans Mike Waltz, Fred Costello and John Ward have been duking it out over who will be the better agent for Trump’s agenda.

Waltz, an Afghan war veteran and onetime aide to former Vice President Dick Cheney, led in a survey conducted by St. Pete Polls earlier this month, which found him ahead of Ward, 40 percent to 21 percent, with Costello at 16 percent. Waltz and Ward have both been effective fundraisers, each raising over $1 million as of Aug. 8, the end of the pre-primary reporting period. But Costello, a former state representative, is keeping things interesting with the backing of Trump ally and outgoing Florida Attorney General Pam Bondi, and the National Rifle Association.

Trump also looms large over the five-way GOP primary in the 15th District to replace retiring Republican Rep. Dennis A. Ross. Former state Rep. Neil Combee has sought to capitalize on his connection to the president, certified by a 2017 appointment to a Department of Agriculture post. That position was weakened when an anonymous website dredged up his Facebook posts criticizing Trump before the 2016 election. He nevertheless held a slim lead in an Aug. 24 St. Pete Polls survey, which found him leading state Rep. Ross Spano 32 percent to 29 percent among likely Republican voters. 

In the 17th District, vacated by GOP Rep. Tom Rooney, the conservative Club for Growth is backing state Sen. Greg Steube and commissioned a poll in mid-August that put him up 39 percent to 16 percent over state Rep. Julio Gonzalez, who has the support of Florida GOP Sen. Marco Rubio. Those endorsements signal another proxy fight between dueling wings of the GOP this primary season. The Conservative Leadership Alliance has spent $200,000 against Steube, who also has the NRA endorsement. Both candidates had raised about a half a million dollars by Aug. 8. A third candidate, Vietnam War veteran Bill Akins, had just $17,000 in the bank.

Democratic primaries 

Three Democratic incumbents, all freshmen, are facing primary challenges that have earned some attention, especially because one of them comes from a controversial former congressman looking for a comeback.

In the 9th District, former Rep. Alan Grayson is challenging Democratic incumbent Darren Soto, who succeeded him after he ran unsuccessfully for Senate in 2016. Soto, the first Florida congressman of Puerto Rican descent, ended the pre-primary reporting period with less cash on hand than his opponent. But Grayson remains more than $2 million in debt from his previous campaigns.

In the 5th District, former Jacksonville Mayor Alvin Brown is trying to unseat Democratic incumbent Al Lawson. Brown is trying to make guns a salient issue in the race. In a statement after the shooting in Jacksonville this weekend, he criticized Congress for only offering “thoughts and prayers” in the wake of mass shootings. Brown has the backing of Missouri Rep. Emanuel Cleaver II, the former chairman of the Congressional Black Caucus, and Martin Luther King III. He called Lawson “Trump’s favorite Democrat” in a TV ad earlier this year that used footage of Lawson applauding during Trump’s State of the Union address. The congressman has raised more money and ended the pre-primary reporting period with more cash in the bank. 

In the 7th District, freshman Rep. Stephanie Murphy faces a challenge from the left in lawyer Chardo Richardson. He’s been endorsed by Alexandria Ocasio-Cortez, who upset House Democratic Caucus Chairman Joseph Crowley in a New York primary in June. But Murphy has overwhelmed her primary opponent in fundraising — $2.4 million to $40,000 for Richardson through Aug. 8. 

In the Miami-area 27th District, Donna Shalala, who was Health and Human Services secretary under President Bill Clinton, shook up the field in one of Democrats’ best pickup opportunities this cycle when she made a late entry and has led in most polling. Her entrance even pushed the candidate endorsed by EMILY’s List to switch to the neighboring 25th District, and the abortion rights group is now behind Shalala. Her closest competition has been state Rep. David Richardson, who’s trying to be the most progressive candidate in the race (openly calling for Trump’s impeachment in his ads) and has attacked Shalala for being too conservative for the district.

Oklahoma runoff

Oklahoma Republicans will select a likely new member of Congress on Tuesday to replace former GOP Rep. Jim Bridenstine, now the NASA administrator. Former Tulsa County District Attorney Tim Harris and businessman Kevin Hern are competing in a GOP primary runoff. The winner would be in a strong position to win in November, with Inside Elections rating the general election Solid Republican.. The winner in November will also serve out the remainder of Bridenstine’s term. 

Correction 9:10 a.m. | An earlier version of this story misstated the second- and third-place finishers in the most recent survey by St. Pete Polls of the Republican primary in Florida’s 6th District. John Ward was in second place with 21 percent, followed by Fred Costello with 16 percent.