The 10 California races Democrats hope hold the golden ticket to a House majority

They'll need to take over handfuls of districts in a few key states in order to get over the top. Democrats can put a significant dent in their goal by doing well in California, where there are at least nine vulnerable Republican seats and where the party can win one-third of the seats necessary for a House majority alone.

But, the top-two primary system is putting pressure on the Democratic Party to make sure their candidates finish first or second in each competitive district on Tuesday, and not get locked out of the general election.

The Democratic Congressional Campaign Committee has a list of more than 100 takeover targets, including 10 seats in California. And seven of those are districts where Hillary Clinton outperformed Donald Trump in the 2016 presidential election.

Here's a closer look at the 10 key House races in California:

4th District

National security strategist Jessica Morse, a Democrat, has kept pace with GOP Rep. Tom McClintock in fundraising and should finish second in the primary. Trump won the district with 54% in 2016, but the race should be regarded as competitive in November. Inside Elections rating: Likely Republican.

10th District

Four Democrats are vying for the second slot in the primary and the right to face GOP Rep. Jeff Denham in November. Venture capitalist Josh Harder, third-time challenger Michael Eggman, Riverbank Mayor Virginia Madueño, and Modesto School Board President Sue Zwahlen have paths to victory. The Democratic nomination is important considering Clinton carried the district with 52%. Inside Elections rating: Tilt Republican.

21st District

GOP Rep. David Valadao has been driving Democrats crazy because he represents a Democratic-leaning district that Clinton and President Barack Obama carried in previous presidential races. Chemical engineer T.J. Cox switched from the 10th District and will finish second in the primary, but it's still unclear if he's strong enough to defeat the resilient congressman. Inside Elections rating: Likely Republican.

22nd District

Fresno County Deputy District Attorney Andrew Janz is likely to finish second in the primary to GOP Rep. Devin Nunes, who's made plenty of new enemies as chairman of the House Intelligence Committee. Nunes had more than $5 million in campaign funds on May 16 and Trump won the district with 52%, but Janz's fundraising improved as Democratic donors viewed the congressman as a Trump defender. Inside Elections rating: Solid Republican.

25th District

Non-profit executive Katie Hill and 2016 nominee Bryan Caforio are the top two Democrats battling for second place in the primary and the right to face GOP Rep. Steve Knight in the general election. Clinton won the district with 50%, so the seat is a top Democratic target, but the Los Angeles media market makes it an expensive endeavor. Inside Elections rating: Tilt Republican.

39th District

Democrats are at risk of not getting a candidate into the general election in an open-seat district Clinton carried with 52%. Former GOP Assemblywoman Young Kim looks likely to finish first, while lottery winner Gil Cisneros, insurance executive Andy Thorburn, refugee-turned-Wall Street analyst-turned-pediatrician Mai-Khanh Tran, and Obama appointee Sam Jammal battle on the Democratic side. Two other Republicans, Orange County Supervisor Shawn Nelson and former state Senate minority leader Bob Huff could pull enough from Kim to allow to Democrats to finish first and second, but that is less likely. Inside Elections rating: Toss-Up.

45th District

A Democrat will finish second to GOP Rep. Mimi Walters, it's just not clear which one. UC Irvine law professors Katie Porter and Dave Min, Obama White House technology adviser Brian Forde, and Kia Hamadanchy, a former aide to Ohio Sen. Sherrod Brown, are running credible campaigns. Clinton won the district in 2016, so the congresswoman is a Democratic target. Inside Elections rating: Lean Republican.

48th District

Democrats are concerned that GOP Rep. Dana Rohrabacher and former GOP state Assemblyman Scott Baugh will finish first and second in the primary, leaving Democrats without a candidate in the general election in a district Clinton carried. National Democrats have rallied behind wealthy realtor/former Republican Harley Rouda, but biologist Hans Keirstead and attorney Omar Siddiqui are running credible campaigns. Inside Elections rating: Tilt Republican.

49th District

Crowded fields for both parties could result in two candidates from each side, or one of each, finishing first and second in the race to replace GOP Rep. Darrell Issa. Board of Equalization member/former Assemblywoman Diane Harkey and Assemblyman Rocky Chavez are the top Republicans, but San Diego County Supervisor Kristin Gaspar is running as well. Environmental attorney Mike Levin, 2016 nominee Doug Applegate, and former Clinton campaign aide Sara Jacobs are the top Democrats. Clinton won the district with 51%, so it's a top Democratic target. Inside Elections rating: Toss-up.

50th District

Trump won the seat comfortably in 2016 but GOP Rep. Duncan Hunter is under investigation for potentially misusing campaign funds, putting his seat in play. National Democrats are most excited about retired Navy SEAL Josh Butner, but former Obama administration aide Ammar Campa-Najjar won the state party endorsement and could finish second. Inside Elections rating: Likely Republican.