BILLINGS — Montana Republicans were to consider a proposal to close future primary elections to non-party members during a three-day convention beginning Thursday in Billings.

Following the June 3 primary, some members of the GOP’s conservative wing complained Democrats crossed party lines to bolster the chances of moderate Republicans in some contested races.

Matthew Monforton of Bozeman, Republican candidate for House District 69, is circulating a proposal to limit future Republican primaries to party members only. He said that would ensure “liberal Republicans” don’t benefit from outside support.

The proposal comes as moderate and conservative Republicans have maneuvered for dominance over a party that currently holds few statewide offices.

Rep. Rob Cook of Conrad, who prevailed over a more conservative challenger on June 3, says Monforton’s proposal is “ludicrous” and threatens to isolate the party from voters.

“It’s like the game all losers play. Rather than admit you might have some problems with your message, you redefine the rules to protect the existing power structure,” Cook said.

Monforton said the closure of future primaries could be accomplished either through legislative action or a lawsuit, based on the premise that Republican voters have the right to choose Republican candidates. He predicted limited success in the Legislature, due to anticipated opposition from some lawmakers and the potential for Gov. Steve Bullock, a Democrat, to veto any bill that passed.

That leaves a lawsuit in federal court as the most viable option, Monforton said.

“The issue our party has to decide is, are we going to be the party of Lincoln and Reagan, or a party of the teachers’ unions,” he said. “Open primaries infringe on the First Amendment political rights of political parties to associate with their own voters.”

Monforton said a similar effort was successful in Idaho, following frustration over Democrats and union members being told to vote for moderate Republicans in the primary, then switching their support to Democratic candidates in the general election.