Longtime Pennsylvania Republican Rep. Bill Shuster's retirement has opened the floodgates for primary challengers to vie for his vacant seat. Tonight, eight Republicans are competing in the GOP primary for this House seat in Pennsylvania's 13th Congressional District.

Two notable conservatives are running: State Rep. Stephen Bloom, who has been endorsed by the House Freedom Caucus, and Art Halvorson, a retired Coast Guard captain who previously challenged Shuster and came within 1,600 votes of defeating him in the 2016 Republican primary.

They are running against six other candidates including a state senator, a physician, a retired colonel, an alpaca farmer, a businessman, and a former marine.

Pennsylvania uses a closed primary system, meaning that voters must be registered party members to vote in a party primary. The polls close at 8 p.m. ET.

Live results: