Four states are holding primaries Tuesday, while California voters will select a replacement for former Speaker Kevin McCarthy, giving Republicans a little more breathing room in the House.

With two Republicans competing in a special election in California’s 20th District, the GOP is sure to add a new member to its slim House majority. And voters in Georgia, Oregon, Kentucky and Idaho will head to the polls for primaries. All of the action is focused on House races, which will set matchups in key battlegrounds and decide likely future lawmakers in less competitive open seats. 

Polls close in Kentucky at 6 and 7 p.m. ET, with the state split into two time zones; 7 p.m. ET in Georgia; 10 and 11 p.m. ET in Idaho; and 11 p.m. ET in California. Oregon conducts its elections entirely by mail, and ballots must be returned or postmarked by 11 p.m. ET Tuesday. 

Here are four things to watch in Tuesday’s elections: 

Kevin McCarthy’s replacement

Republicans in Washington, D.C., will get a gift out of Tuesday night’s elections — a reinforcement from California, where voters are casting their ballots in a special election between Assemblyman Vince Fong and Tulare County Sheriff Mike Boudreaux.

Both candidates are Republicans, meaning the GOP will have 218 members to the Democrats’ 213 once the winner is sworn in, with four vacancies. That means Republicans will be able to afford two defections rather than the current one with a full House in attendance. 

California puts all candidates on the same primary ballot regardless of party affiliation, and in a special election, if no candidate wins a majority of the vote, the top two vote-getters move onto a general election. 

The winner of the special election will serve out the rest of McCarthy’s term. McCarthy resigned at the end of last year after he was ousted as speaker. Fong and Boudreaux will also face off in November in the regularly scheduled general election. 

McCarthy endorsed Fong, who used to work for him. And Fong finished with the most votes in the March primary. 

Oregon battles 

Oregon is home to three competitive House districts where matchups will be set Tuesday. 

Monique DeSpain, an attorney and Air Force veteran, is the top fundraiser in the GOP field in the 4th District to take on Democratic Rep. Val Hoyle. The leading Republican fundraiser vying to take on Democratic Rep. Andrea Salinas in the 6th District is businessman Mike Erickson, who lost to her by nearly 3 percentage points in 2022. 

But most of the primary action has centered on the 5th District, where GOP Rep. Lori Chavez-DeRemer is running for re-election. 

The Democratic Congressional Campaign Committee has taken the rare step of taking sides in the primary to boost state Rep. Janelle Bynum over attorney Jamie McLeod-Skinner. Chavez-DeRemer beat McLeod-Skinner by 2 points in 2022, even though Joe Biden carried the district by 9 points in 2020, according to calculations from Daily Kos Elections. 

Multiple outside groups have engaged in the race, with a pro-Bynum group, Mainstream Democrats, launching an ad highlighting reports that McLeod-Skinner mistreated her campaign staff. 

McLeod-Skinner, meanwhile, has gotten a boost from a group called Health Equity Now, which has launched ads touting her support for “Medicare for All” legislation. Some Democrats have suggested the group could be an attempt by Republicans to meddle in the primary, because the group’s ad buying firm is typically used by GOP candidates, according to The Washington Post. 

Sister act

Outside groups have also engaged in the Democratic primary to replace retiring Rep. Earl Blumenauer in Oregon’s deep-blue 3rd District. 

The primary field is crowded, with the top candidates including former Multnomah County Commissioner Susheela Jayapal, whose sister, Pramila, represents Washington’s 7th District in Congress and chairs the Congressional Progressive Caucus. 

Jayapal has nabbed some high-profile endorsements, including Sen. Bernie Sanders’, but she has faced attacks on the airwaves from an outside group called Voters for Responsive Government. 

314 Action, which backs candidates with STEM (science, technology, engineering and mathematics) backgrounds, has also launched ads to boost state Rep. Maxine Dexter, a physician. Dexter has led the field in fundraising, followed by Jayapal and Gresham City Council member Eddy Morales. 

Republican primaries to watch 

There are also a handful of GOP primaries worth keeping an eye on, albeit in districts that aren’t expected to be competitive in the fall. 

In Kentucky’s 4th District, GOP Rep. Thomas Massie faces a primary challenge from two main opponents who have been critics: attorney Eric Deters and Michael McGinnis. 

Massie has made some enemies in Congress. He joined the unsuccessful effort to oust Speaker Mike Johnson, R-La., over criticism of Ukraine aid and funding for a controversial intelligence tool. He was one of the few members of Congress to endorse against former President Donald Trump (he backed Florida Gov. Ron DeSantis). And in 2020, his opposition to an emergency pandemic relief bill prompted Trump to call for him to be removed from the party. 

Massie is the heavy favorite, but the primary has drawn some significant spending from a super PAC affiliated with GOP Sen. Rand Paul of Kentucky (which backs Massie) and from the pro-Israel United Democracy Project, which has said it isn’t playing directly in the primary but is running ads to criticize Massie’s Israel policies (Massie is seen as a potential future candidate for statewide office). 

In Idaho, GOP Rep. Mike Simpson has hit the airwaves ahead of his primary, and he has gotten some outside help from Defending Main Street, a super PAC tied to the Republican Main Street Partnership. Simpson’s best-funded primary opponent, financial adviser Scott Cleveland, has partly self-funded his campaign. 

In Georgia, Trump’s endorsement is on the line in the 3rd District, where he is backing Brian Jack, his former White House political director, to replace retiring GOP Rep. Drew Ferguson. Jack has been the top fundraiser in the race through April, and he has been boosted by significant outside group spending, as well. His opponents include state Sen. Mike Dugan, former state Sen. Mike Crane and military veteran Philip Singleton. 

There’s also a Republican primary for the right to face off against Democratic Rep. Sanford Bishop in Georgia’s 2nd District. Bishop isn’t expected to be vulnerable in a general election: He won re-election in 2022 by 10 percentage points, and Biden won the district in 2020 by a similar margin, according to data from Daily Kos Elections.

The GOP primary hasn’t drawn much spending. The field includes Chuck Hand, who pleaded guilty to a misdemeanor related to his conduct during the attack on the U.S. Capitol on Jan. 6, 2021.