OLYMPIA — The Republican candidate for U.S. Senate in Washington state said Thursday that he does not support Donald Trump as his party’s presumed presidential nominee, and won’t vote for president in November unless a conservative third-party alternative comes forward.

Chris Vance, who is running against incumbent Democratic U.S. Sen. Patty Murray, is the latest of several Republican officials in the state who have become vocal in their opposition to Trump.

“This is a difficult and unprecedented time for our party, and I take no joy in not supporting the presumptive Republican nominee, but I must place conscience and principle ahead of party,” Vance read from a prepared statement at a Seattle news conference.

Vance said that he would vote for John Kasich, who dropped out of the presidential race Wednesday, in Washington state’s presidential primary on May 24.

Republican Sen. Don Benton, Trump’s state campaign chairman, said that it was Vance’s right to support whomever he wanted, but said that he thinks Vance’s stance clearly doesn’t reflect what Republican voters want.

Benton said that Vance and other Republicans opposed to Trump are the “typical Republican establishment pushing back against a candidate that they know will not cower to special interests.”

“When your power is threatened, you push back,” Benton said.

On KUOW radio Wednesday, Rob McKenna, the former attorney general in Washington and a former Republican gubernatorial candidate, called Trump “a demagogue and an opportunist with no real foundation in principles or values” and said that his presumed nomination is bad for the Republican Party.

“Trump came in and hijacked our party,” McKenna said.

McKenna expressed concern that Trump could negatively affect other Republicans running on the Washington state ballot.

A survey last month from independent pollster Stuart Elway found that the so-called down ballot effects varied depending on the presidential candidate at the top of the ticket, with Trump having the largest negative effect on Washington state congressional candidates who endorsed him.

While Republicans have a strong presence in the state Legislature and hold four of the state’s 10 seats in the U.S. House, Washington voters usually select Democrats in statewide races. The last time a Republican won a U.S. Senate seat was 1994 and the last time a Republican was elected governor was in 1980.

The state’s current lone Republican statewide elected official, Secretary of State Kim Wyman, says that because of the responsibilities of her role in overseeing elections, she won’t be weighing in one way or another on the presidential race. Wyman, who faces a Democratic challenger in November, said she realizes her stance may be used against her.

“My job is to be impartial, and I’m going to do that,” she said.

Several other Republicans in the state have also said they can’t support Trump, most recently Sen. Steve Litzow, who posted a statement to his Facebook page Wednesday that a Trump presidency “would be detrimental to our nation’s spirit, economy, safety, and world standing.”

Republican gubernatorial candidate Bill Bryant has been silent on the presumed nominee, and did not return phone calls or emails seeking comment.