Republican primaries for the Indiana Senate will take place on May 5, 2026. The general election is on November 3, 2026.

The Indiana Senate is one of 88 state legislative chambers with elections in 2026. There are 99 chambers throughout the country. Twenty-five of the Indiana Senate's 50 seats are up for election in 2026.

Before Indiana's mid-decade redistricting effort failed in the state Senate in December 2025, President Donald Trump (R) wrote in a Truth Social post: "Anybody that votes against Redistricting, and the SUCCESS of the Republican Party in D.C., will be, I am sure, met with a MAGA Primary in the Spring." Twenty-one Republicans joined the chamber's 10 Democrats in voting against redistricting.

Trump endorsed several primary challengers running against Republican senators who voted against redistricting:

According to the Indiana Capital Chronicle's Tom Davies, a group affiliated with U.S. Sen. Jim Banks (R) released radio and digital advertisements against the Republican senators who opposed redistricting in March 2026: "The ads that started appearing last week follow the theme that the senators opposed 'President Trump’s plan to remove liberal Democrats from Congress' along with knocking them for votes on gasoline or property taxes and foreign land ownership."

WFYI's Caroline Beck wrote, "Former Indiana Republican Gov. Mitch Daniels is lending his political will and name power to help campaign for current Republican state lawmakers being primaried by Trump-supported candidates." Daniels said, "I think it's important that people who are fine public servants and have shown it in other contexts, who stood up for a principle here and showed bravery in so doing, that ought to be rewarded, not punished, and it's certainly not going to be punished by people from several hundred miles away who couldn't find Indiana with a road map."

Heading into the elections, Republicans had a 40-10 majority in the Senate. The state has had a Republican trifecta since 2011.

Of the 20 contested Republican primaries, Ballotpedia designated 11 as battlegrounds. Ballotpedia makes battleground designations for state legislative primaries based on electoral competitiveness and political context. Criteria include open seats, incumbents' prior electoral performance, and the presence of organized or experienced challengers.