After a month on the sidelines, the 2026 primary season is back with a vengeance. A dozen states from coast to coast hold primaries or runoffs in May, and the results of those nomination contests may ultimately determine the outcomes of November's midterm elections, when Republicans will be defending their slim Senate and razor-thin House majorities. Also on the line: President Donald Trump's immense sway over the GOP, as his endorsements in key races will be tested.
The primary calendar kicks off with Indiana and Ohio on May 5, followed by Nebraska and West Virginia on May 12. Louisiana holds its nominating contest on May 16, while the busiest day arrives three days later when Alabama, Georgia, Idaho, Kentucky, Oregon and Pennsylvania all hold primaries. Texas wraps up May with runoff showdowns on May 26.
What the Right Is Saying
Trump's allies argue that the primary challenges are necessary to ensure Republicans are committed to advancing the president's agenda. Turning Point USA's political wing and the Club for Growth have invested millions in Indiana's primary battles.
"We've got to change those old-style Republicans, put in people who will fight, fight against the Democrat gerrymandering," Club for Growth President David McIntosh told Fox News Digital. McIntosh, a former congressman from Indiana, said "I want to see my state do the right thing."
The intra-party battle is framed by Trump supporters as a test of fealty versus more traditional conservatives who have sometimes resisted the president's priorities. In Louisiana, where Sen. Bill Cassidy faces challenges from Rep. Julia Letlow and former Rep. John Fleming, Trump's endorsement of Letlow signals the president seeks accountability for Cassidy's 2021 vote to convict him in the impeachment trial.
In Kentucky's 4th Congressional District, Trump-backed Ed Gallrein is challenging Rep. Thomas Massie, who has been one of the president's most vocal GOP critics in Congress.
What the Left Is Saying
Democrats are watching the Indiana redistricting fight closely, noting that the eight GOP state senators targeted by Trump voted against a map that would have given Republicans two additional right-leaning House seats. The outcome could shape competitive House races heading into November.
Progressive groups argue that Trump's aggressive primary interventions reflect his priority of consolidating control over the Republican Party rather than building a coalition capable of winning general elections. "These primaries are about punishing Republicans who dared to follow their own judgment on basic questions of fair representation," one Democratic strategist told Fox News Digital, speaking on background.
On Ohio's Senate race, Democrats point to polling showing former longtime Sen. Sherrod Brown competitive in a state Trump carried by 11 points in 2024. The race is considered among a handful nationally that could determine control of the Senate chamber.
What the Numbers Show
The May primary calendar features contests across a dozen states with direct implications for November's balance of power:
Indiana (May 5): Eight GOP state senators face Trump-backed challengers after voting against redistricting legislation that would have added two Republican-leaning House seats to the state's delegation.
Ohio (May 5): Vivek Ramaswamy, backed by Trump and a former 2024 presidential candidate, is favored in the gubernatorial primary. The Senate race features appointed Republican Jon Husted versus former Democratic Sen. Sherrod Brown, who must serve the final two years of Vice President JD Vance's term.
Louisiana (May 16): If no Senate candidate reaches 50%, top two finishers advance to a June 27 runoff. Trump has endorsed Letlow over incumbent Cassidy.
Kentucky (May 19): Massie's primary challenge from Gallrein tests whether Trump's endorsement can unseat an established congressman who has frequently opposed the president's positions.
Ohio shifted significantly rightward, with Trump winning by 11 points in 2024. However, Senate and gubernatorial races are expected to remain competitive despite the partisan lean.
The Bottom Line
May's primary season will provide early indicators of Trump's continued grip on the Republican Party and whether incumbents who have sometimes diverged from his positions can survive challenges from within their own party. The Indiana redistricting fight is particularly watched as a test of whether traditional conservative legislators or Trump-aligned challengers will control state-level Republican politics heading into the midterms.
The outcomes will shape ballot lines across a dozen states, determining which candidates face off in November when Republicans seek to maintain their slim Senate and House majorities against Democratic efforts to flip at least one chamber. Voters in Indiana, Ohio, Louisiana and Kentucky should pay particular attention to results from May 5 through May 19 as the primary picture comes into focus.