HELENA, Mont. -

Three former Montana Republican Party chairmen have taken the unusual step of uniting to publicly oppose former state Sen. Ryan Zinke's U.S. House bid.

State Sen. John Brenden of Scobey, former U.S. Rep. Rick Hill and former gubernatorial candidate Ken Miller released a statement Monday saying the Whitefish Republican's views aren't conservative enough.

They take issue with Zinke's past legislative votes on issues such as natural-resource development and question his ties to a political-action committee he founded.

Zinke says the three see him as a threat to win the five-candidate primary over their favored candidates. He says he is fiscally conservative, pro-business, anti-abortion and supports gun rights.

Brenden and Hill are supporting other candidates in the June 3 primary. Miller says he supports any candidate other than Zinke.