Republican candidate and state Sen. Tom Campbell announced Wednesday he will drop out of the race to fill North Dakota’s House seat and endorsed one of his primary opponent challengers.

Campbell was one of four candidates running to fill Rep. Kevin Cramer’s seat for the at-large district. Cramer announced in February he would leave his House seat to challenge Sen. Heidi Heitkamp.

In his statement, Campbell said it was important for Republicans to be united in the face of Democrats who are excited to win back the house.

“Across the country, Democrats are energized and determined to win back the House and derail Republican’s conservative change agenda,” he said in his statement.

Campbell put his weight behind fellow state Sen. Kelly Armstrong, whom the state party also endorsed.

“We need to make sure Republicans keep North Dakota’s congressional seat,” he said. “I’m confident Kelly will fight for conservative values in Washington.”

Campbell announced earlier this week he would challenge Armstrong in the state’s primary in June.

When he filed for candidacy, he compared himself to President Donald Trump.

“Like President Trump, I’m a Washington outsider who will drain the swamp,” he said. “I’m a self-made businessman who can’t be intimidated by the lobbyists or special interests.”

Unlike Trump though, Campbell currently holds a state Senate office but never mentioned it.

Inside Elections with Nathan L. Gonzales rates North Dakota’s at-large district Solid Republican.