Montana Republicans have resolved to close their primary elections to outsiders and adopt a runoff system for the general election.

The proposals were adopted Saturday by a group of roughly 200 delegates at the party's election-year convention in Billings. That followed a contentious internal debate that highlights the deep divisions within the state party.

The changes will not go into effect automatically. They would have to be approved by the state Legislature or mandated by a successful federal lawsuit.

Support for closed primary elections was strongest among conservatives. They've complained bitterly that some Democrats crossed over during the June 3 primary to vote for moderate Republicans.

Critics warned the move will alienate voters. Great Falls Rep. Steve Fitzpatrick says candidates should concentrate instead on running stronger campaigns.