Intraparty tensions shape the 2026 midterm primary landscape

In a highly polarized political world, where more congressional districts than ever before are considered “safe” for one party or the other, real change plays out in congressional primaries. That’s why, for the past decade, Brookings has studied House and Senate primaries, looking for fissures in each political party and analyzing the impact on electoral success and governing. Two questions loom large in the current primary season. One is whether Trump’s power and influence in the Republican Party is waning now that he is in danger of becoming a lame duck president. The other is whether the left wing of the emerging post-Trump Democratic Party has gained power and influence as a younger generation comes into the electorate. As the primary season unfolds, with some primaries in May but many more throughout the summer, and as redistricting battles wind their way through the courts, here’s what we know so far. 

Republican primaries as a Trump referendum

On May 5, Indiana primary voters delivered a solid win to President Trump. Seven incumbent Republican state senators who had blocked Trump’s request to draw new congressional lines that would yield more Republican districts found themselves the object of Trump’s promise for political retribution and were challenged by Trump-endorsed candidates. It created one of the clearest tests between the MAGA wing of the Republican Party and its more traditionally conservative counterpart. It was a big win for Trump, with five of the seven MAGA challengers winning their races against the incumbents who had challenged his position on redistricting. 

In addition to Indiana, three more contests are coming up in May that will test Trump’s strength within his party. The next race to consider will be the Louisiana Republican Senate primary on May 16, where incumbent Sen. Bill Cassidy (R-La.) will face Trump recruit Rep. Julia Letlow (R-La.). Cassidy has been on Trump’s radar ever since he voted to impeach him following the Jan. 6 insurrection. The discord increased when Cassidy, a medical doctor, pointedly questioned Trump’s nominee to head the U.S. Department of Health and Human Services, Robert F. Kennedy Jr., over Kennedy’s unorthodox stances on vaccines and other health issues. 

Another high-profile race to watch is Kentucky on May 19, where incumbent Rep. Thomas Massie (R-Ky.) drew Trump’s ire by opposing his position on a short-term funding bill and by joining Rep. Ro Khanna (D-Calif.) in calling for the Justice Department to release the Epstein files. Massie faces Ed Gallrein, a farmer, former Navy SEAL, and political newcomer. If Cassidy and Massie survive primary challenges from Trump’s hand-picked candidates, more members of Congress may vote against President Trump’s interests in the upcoming session. This could indicate a decline in Trump’s hold over his party. 

Finally, Texas will host a high-profile Republican run-off election on May 26, following a heated early March primary between incumbent Sen. John Cornyn (R-Texas) and Attorney General Ken Paxton. So far, the race appears tied with perhaps a slight edge to Paxton. Both candidates are strong supporters of President Trump, as would be expected in this very conservative state, but it seems as if Paxton is stylistically more MAGA than Cornyn. In fact, the Paxton campaign is trying hard to inherit the Trump mantle and paint Cornyn as a RINO (Republican in Name Only). Paxton’s support comes largely from non-college-educated voters, while Cornyn’s voters tend to be college educated. A Paxton win will not be as clear-cut a signal about Trump as other races in May. Early on, Trump had promised to endorse one of the two, but as the race has remained close in early May, Trump has held off on an endorsement. A win for Paxton, who has been plagued by scandals, may open the door for a Democrat to win a Senate race in Texas for the first time since the early 90s. 

A special election in New Jersey’s 11th Congressional District earlier in 2026 began with what looked like a big win for the left-wing candidate. In February, Analilia Mejia, a progressive organizer and former staffer for Sen. Bernie Sanders’ (I-Vt.), achieved an upset victory by defeating former Rep. Tom Malinowski (D-N.J.), who had entered the race as the front-runner. She then went on to a landslide win in an April special election against Republican Joe Hathaway. However, special elections are notoriously low-turnout affairs, and the special primary there saw a huge influx of cash from the American Israel Public Affairs Committee (AIPAC), which sought to unseat Malinowski over his votes to condition aid to Israel. However, as many were quick to point out, AIPAC’s bet backfired and split the vote among the more traditional candidates, allowing Mejia to win the special primary and later the special election, despite her own criticism of U.S. aid to Israel. Mejia must run again in June in a Democratic primary against three lesser-known candidates, then face Hathaway again in November in what will likely be a higher-turnout election with a less certain outcome.  

In the Democratic Senate primary in Texas, Rep. Jasmine Crockett (D-Texas) faced state Rep. James Talarico. Crockett, a Black former civil rights attorney and outspoken critic of Trump, entered the primary as the front-runner. Republicans worked to liken her to Rep. Alexandria Ocasio-Cortez (D-N.Y.) and other progressives. Although Talarico was just as liberal as Crockett on many issues, his style was more measured. As a Presbyterian minister, he campaigned in Republican areas of the state and quoted the Bible often. In fact, one of his most famous quotes is “God is nonbinary.” In this high-visibility primary, Crockett won most of the state’s Black vote, but still lost by 6 percentage points.  

Also in March, the Democratic primary in Texas’ 34th Congressional District featured a race between incumbent Rep. Vincente Gonzalez (D-Texas), a moderate Democrat, and Etienne Rosas, a Democratic socialist. Gonzalez beat Rosas by 25 points, although large margins are not unusual when an incumbent is seeking reelection. 

Another way to assess the strength of the party’s left flank is to look at the candidates who have been endorsed so far this year by Sen. Bernie Sanders: three Senate candidates and 11 House candidates in Democratic primaries. Sanders’ Senate picks won’t face voters until the summer, so it’s unclear how they will do. But he has had one win already. His pick in Maine, young oyster farmer and first-time Senate candidate Graham Platner, has been running a competitive campaign. In fact, seeing the writing on the wall, Gov. Janet Mills (D-Maine), who has won four statewide elections and was expected to be the strongest candidate, dropped out of the race. And early polling shows Platner running ahead of longtime Sen. Susan Collins (R-Maine).

In primaries for House races, Sanders’ candidates lost in Illinois’ 2nd and 8th congressional districts, North Carolina’s 4th Congressional District, and Utah’s 1st Congressional District. He did pick up wins in Ohio’s 7th Congressional District with his endorsement of Brook Park City Councilman Brian Poindexter and in New Jersey with his endorsement of Mejia. 

The success or failure of left-wing candidates will have a major influence on presidential campaigns. As would-be 2028 contenders read the tea leaves from congressional primaries, they will look to see whether the left wing of the party is winning nominations and converting them into general election victories.

The stakes beyond the primaries

When the dust settles in November, the presidential race will begin in earnest. Each party will pour over midterm election results. Will Trump still maintain his control over the Republican Party? If so, how did his party perform? For a decade now, many have been wondering whether a more traditional Republican Party will reassert itself. The conclusion will determine not just what the post-Trump Republicans stand for but which candidates enter the presidential race. 

On the Democratic side, will the party veer left, as it appears to have done in high-profile races like New York City’s mayoral contest? And if so, will it cost them in a general election, dooming them to minority status? 

We will revisit these questions as more campaigns are fought and settled.