What to know and who to watch in the next 7 state primaries

Voters in seven states head to the polls on Tuesday to pick party nominees for some of the nation's most competitive House seats -- and their choices will be shaped by key forces, like redistricting, that will help decide who controls Congress next year.

California, Iowa, Mississippi, Montana, New Mexico, New Jersey and South Dakota are next to vote in the ongoing primaries.

One of the marquee developments will be the outcome in brand new congressional districts, which were based on the last census and each state's rules about who drew the new maps. In most cases, the state legislatures were responsible, with observers tracking how the new lines across the country favor one party over another -- and with some new maps enduring rounds of controversy and judicial review.

The candidates for some of these new seats highlight fluctuating intraparty dynamics for both Democrats and Republicans. The latest batch of primaries also features some of the most endangered incumbents from either party.

California Republican Reps. Mike Garcia -- who voted not to certify the 2020 election results -- and David Valadao -- one of 10 Republicans who voted to impeach Donald Trump in the wake of Jan. 6 -- are attempting to keep their seats in districts that absorbed a near 12-point edge in Democratic voter registration after the state's latest decennial redraw.

Meanwhile, in Iowa, Democratic Rep. Cindy Axne is grasping at her swing district as her state has moved further and further right.

Fellow Democratic incumbent Tom Malinowski, of New Jersey, is in a long-shot fight to keep hold of his newly GOP-favorable 7th Congressional District, which was redrawn in order for the state's Democrats to bolster a number of their other vulnerable lawmakers.

The contest for New Mexico's second congressional seat highlights a newly formed district that shifted in 2020 from Trump to Joe Biden by 17 points. It'll be a toss-up race between incumbent Republican Rep. Yvette Herrell and front-runner Gabe Vasquez, a Mexican-born former Las Cruces councilman and former aide to Sen. Martin Heinrich. In California, Democratic Rep. Mike Levin's 49th District was recently made slightly more Republican.

Redistricting drew incumbent Republican Rep. Michelle Steel into the same district as Democratic fundraising powerhouse Rep. Katie Porter in Orange County, California, forcing the former to move over to the 45th District.

Concerns about crime and policing will also play out in some primaries. San Francisco District Attorney Chesa Boudin faces a recall, with his opponents arguing he has not done enough to combat criminals in the city while his supporters say he's trying to fix and reimagine law enforcement. San Franciscois one of the most liberal cities in America and if voters do kick out Boudin, it could be a telling sign of how far progressive prosecutors can go in metro areas.

South of San Francisco, crime is also having an impact in the Los Angeles mayoral race. where billionaire real estate developer Rick Caruso has seen his profile rise. Caruso, a former Republican and self-described "centrist," has promised to invest more in L.A.'s police department and focus on public safety. The other leading contender in the race is Democratic Rep. Karen Bass, who has served six terms in Congress and was also on the long list to be Biden's vice presidential running mate. Bass has touted her own extensive plans for crime in the city, reflecting how it remains top of mind for local voters.

California's primary will shift light onto another race: GOP House Minority Leader Kevin McCarthy is up for reelection in the 20th Congressional District. On Sunday, McCarthy received an endorsement from former President Trump, who called him a "tireless advocate" for his area and a chief opponent of Biden and House Speaker Nancy Pelosi.

But even though he endorsed McCarthy, Trump did not mention supporting McCarthy in his run for speaker should Republicans gain control of the House. McCarthy is widely expected to seek the speakership, should the GOP retake the majority, and Trump's support would be critical.

Last, in Iowa, state Democrats' push to unseat 88-year-old Republican Sen. Chuck Grassley is shaping up to be a major primary battle on Tuesday -- and one that could illustrate disorganization in the party ahead of more fierce fighting for the historically purple state. Former Rep. Abby Finkenauer is in an ever-tightening race against retired U.S. Navy Vice Adm. Mike Franken. While that primary had been intended as an easy win for the well-connected Finkenauer, ballot accessibility hurdles involving the Iowa Supreme Court and some campaign management challenges instead put her into a much more competitive race with Franken. Both will also be up against rural physician Glenn Hurst.