HELENA — Technology entrepreneur Greg Gianforte and musician Rob Quist will square off in a special election to fill the Montana U.S. House seat left vacant by Ryan Zinke’s departure to become President Donald Trump’s interior secretary.

Republicans selected Gianforte over six others Monday night in a special nominating meeting for the May 25 election. Gianforte, a conservative who has never held political office, will be facing another political newcomer in Quist.

On Sunday, the Democrats nominated the 69-year-old who is best known as a singer and guitarist for the Mission Mountain Wood Band.

Gianforte won the majority of the 203 Republican delegates from across the state in a single round of voting after he pledged to back the Trump administration’s policies on issues from increased border protection to repealing the Affordable Care Act.

Gianforte said he was honored and ready to go to work.

“This election will be a referendum on Donald Trump and this administration,” Gianforte said. “We’re going to have national attention, and we need every single person in this room to do everything you can to make sure we win.”

Gianforte, 55, sold his software company RightNow Technologies to Oracle for $1.8 billion in 2011. He is now attempting to rebound from his defeat last November in an expensive governor’s race against incumbent Democrat Steve Bullock.

Even before securing the GOP nomination, Gianforte went on the attack against Quist. Gianforte used a candidate forum earlier Monday to paint Quist as an “out-of-touch liberal” in a state that voted strongly for Trump in November.

Other Republicans also quickly responded to Quist’s ascension. A super PAC called the Congressional Leadership Fund announced it will spend $700,000 on an ad campaign to influence Montana’s May 25 special election. The first spot aired Monday, attacking Quist with the same out-of-touch message as Gianforte’s.

Quist was not available for comment, spokeswoman Tina Olechowski said. The attacks make it clear “the D.C. establishment and Greg Gianforte are running scared of Rob Quist,” she said in a statement.

The state’s Libertarian Party will also nominate a candidate for the special election when its members meet next weekend. All other parties and potential independent candidates were required to submit petitions with at least 14,268 signatures by the close of business Monday.

Secretary of State spokeswoman Morgan Williams said nobody turned in a petition by the deadline, meaning no other candidates will be on the ballot.

Gianforte claimed to have locked up the election well before Monday’s vote while meeting with delegates on a statewide tour since Trump nominated Zinke in December. State Sen. Ed Buttrey, a moderate Republican hopeful, had tried to undermine Gianforte’s support by painting Gianforte as too conservative to appeal to all Montana voters.

Buttrey also said he would not use the U.S. House seat as a stepping-stone for a higher position. Zinke and U.S. Sen. Steve Daines, the last two holders of the seat, both left after one term.

Gianforte said in an earlier interview with The Associated Press that he would seek at least two terms if he wins the special election this year.

That two-term commitment leaves open the possibility of Gianforte running for governor again in 2020, said David Parker, a political scientist for Montana State University.

“If he were to leap to a different seat, it would be the governor’s seat in 2020, which is open,” Parker said. “It’s sensible for Gianforte to run for the House, run for the House again and then governor after that.”