- Eight states including California and New Jersey will hold primary elections Tuesday.
- California, New Jersey and Iowa will be crucial in determining which party controls the House after November's midterm elections.
- Montana voters will also choose the GOP challenger to vulnerable Democratic Sen. Jon Tester.
A slate of primary elections in eight states Tuesday will have perhaps the biggest stakes yet this year in the battle for Congress.
The most populous American state, California, headlines the day's primaries. Democrats are targeting up to 10 Republican-held House seats there, and could flip a significant portion of the 23 GOP seats they need in November's midterms to take control of the House. But an abundance of Democratic candidates running in the state's top-two primary system — which allows the two highest vote-getters regardless of party affiliation to move forward — could lead to the Democrats getting shut out of one or more key swing district general elections.
President Donald Trump stressed the importance of the state's House races in a tweet Tuesday morning urging voters to support Republican candidates. He and House Republican leaders have frequently used California's most prominent Democrat, House Minority Leader Nancy Pelosi, as a midterm attack target against her party.
"Keep our country out of the hands of High Tax, High Crime Nancy Pelosi," the president wrote.
Meanwhile, voters in red Montana will choose a nominee to face Sen. Jon Tester, one of the chamber's most vulnerable Democrats. Five of the states, including California, will start the process of electing governors, as well.
Here are some of the races to watch:
- 48th District: The seat represented by GOP Rep. Dana Rohrabacher is one of three top Democratic targets in which the party risks missing out on the general election. Democrats have spent money aiming to prevent Republican former California Assemblyman Scott Baugh from finishing in the top two. Among Democratic candidates running, the national party prefers businessman Harley Rouda and House Democrats' campaign arm has spent money supporting him. The California Democratic Party has backed stem cell researcher Hans Keirstead.
- 39th District: The district is open due to the retirement of GOP Rep. Ed Royce, and Democrats could fail to make the general election in the competitive area. Former state Assemblywoman Young Kim appears to have the edge among Republicans. Leading Democrats Gil Cisneros, a Navy veteran and education advocate, and businessman Andy Thorburn previously reached a deal to stop attacking one another.
- 49th District: Another top Democratic target, this seat vacated by GOP Rep. Darrell Issa's retirement appears to carry a lower lockout risk than the 48th and 39th districts. Leading Republicans include state Assemblyman Rocky Chavez and former state Assemblywoman Diane Harkey. Contenders on the Democratic side include clean energy advocate Mike Levin, Marine veteran Doug Applegate and former State Department official Sara Jacobs.
- 10th District: Vulnerable GOP Rep. Jeff Denham, who has served in Congress since 2011, hopes to defend his seat again. Possible Democratic challengers include small businessman Michael Eggman, who lost to Denham by about 3 percentage points in 2016, and technology investor Josh Harder.
- 25th District: Democrats hope to unseat GOP Rep. Steve Knight from this district. Potential Democratic nominees include lawyer Bryan Caforio and former nonprofit executive Katie Hill.
- 45th District: Several Democrats are pushing to take on GOP Rep. Mimi Walters in what could be a competitive general election. Ex-Obama administration official Brian Forde and law professor Katie Porter are among the Democrats running for the seat.
- Senate: Dianne Feinstein, the 84-year-old Democratic senator who has served in the chamber for more than two decades, faces a challenge on the left from state Sen. Kevin de Leon. Tuesday will be a major test of whether de Leon's bid has traction.
- Governor: Democratic Lt. Gov. Gavin Newsom is expected to win the primary to succeed term-limited Gov. Jerry Brown. Trump-backed Republican John Cox is trying to secure the second spot.
California has a high-proportion of absentee ballots, so some important races may not be decided for days.
- 2nd District: The retirement of Republican Rep. Frank LoBiondo gave Democrats higher hopes of flipping the swing district. State Sen. Jeff Van Drew appears to be the top Democratic contender, while engineer Hirsh Singh is among the top Republicans.
- 7th District: GOP Rep. Leonard Lance is defending his seat in this district targeted by Democrats. Former Obama administration official Tom Malinowski leads the fundraising race on the Democratic side.
- 11th District: The seat vacated by Republican Rep. Rodney Frelinghuysen's retirement will be highly contested in November. Crowded primary fields have emerged on both sides. Mikie Sherrill, a former federal prosecutor and Navy veteran, easily leads the fundraising race and has support from national Democrats. Republican contenders include state Assemblyman Jay Webber and businessman Peter de Neufville.
- Senate: Former Celgene CEO Bob Hugin is expected to emerge from the state's GOP Senate primary and face incumbent Democratic Sen. Bob Menendez. While New Jersey tilts solidly blue, Menendez's ethics issues have made the race more compelling than it normally would be.
Sen. Jon Tester, a Democrat running in a state Trump won by about 20 points in 2016, is considered one of the most vulnerable senators seeking re-election this year. Tester has only voted with Trump 37 percent of the time, according to FiveThirtyEight — significantly less often than his Democratic colleagues running in other red states.
Most recently, he opposed Trump's choices for secretary of State and CIA director, Mike Pompeo and Gina Haspel, respectively. Trump has repeatedly criticized Tester, most notably for his role in the withdrawal of the president's pick to lead the Department of Veterans Affairs, White House physician Ronny Jackson.
Montana will pick Tester's Republican challenger on Tuesday. The senator was perceived to have gotten a break when Trump chose a possible top contender, Ryan Zinke, to lead his Interior Department.
Potential challengers include State Auditor Matt Rosendale and former Judge Russell Fagg.
- 1st District: GOP Rep. Rod Blum hopes to keep his seat in the Iowa swing district. National Democrats have put their weight behind state legislator Abby Finkenauer, who has easily led the fundraising race among her party's candidates.
- 3rd District: Democrats aim to unseat GOP Rep. David Young in the district. Business owners Eddie Mauro and Cindy Axne are considered the top Democratic contenders for the seat.