SALT LAKE CITY (AP) — U.S. Sen. Mike Lee is scheduled on Wednesday to debate two challengers aiming to unseat him in Utah’s June 28 Republican primary.

Though he represents reliably Republican state, Lee — more than many other red state incumbent senators — is facing serious challenges in this year’s midterm elections.

Former state lawmaker Becky Edwards and Ally Isom, a veteran Utah political staffer, are his two Republican challengers. They have, throughout campaign season, attacked what they describe as his divisive rhetoric and governing style.

In a state where Trump critic Mitt Romney won a Senate seat convincingly four years ago, the race will reflect the extent of shifts underway in the Republican Party and test the durability of the former president’s support.

Lee has shown his support remains strong among Republicans. He received 71% of delegate votes at a party convention in April. The margin would have sealed him the nomination had Isom and Edwards not gathered signatures to qualify for the primary ballot.

The debate is being hosted by Utah’s Republican Party, which withdrew from a debate commission that has historically organized the events. The winner of the primary will take on indepdent candidate Evan McMullin, who won the Democratic Party’s backing at its April convention.