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:
California has a high-proportion of absentee ballots, so some important races may not be decided for days.
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.