OKLAHOMA CITY — Election officials predict turnout will be relatively low across the state for Tuesday’s primary runoffs, although polling places are expected to be a little busier in eastern Oklahoma where four men are vying for a fiercely contested congressional seat.

Two Republicans and two Democrats are in runoffs in the 2nd Congressional District. The contests will decide who advances to the November general election in a race to replace the only Democrat in Oklahoma’s congressional delegation, retiring U.S. Rep. Dan Boren.

Oklahoma has a closed primary system, so only registered Republicans and Democrats can vote for their own primary candidates. The 26 counties that make up the 2nd District are expected to have the heaviest turnout.

Polls are open from 7 a.m. to 7 p.m. in most of the state Tuesday. There are no elections in more than a dozen counties.

On the Republican side, Westville plumbing company owner Markwayne Mullin faces three-term state Rep. George Faught, who owns a carpet cleaning business. Democrats will choose between longtime state and federal prosecutor Rob Wallace and Muskogee seed company owner Wayne Herriman.

Mullin received 42 percent of the vote in a six-man Republican primary June 26, while Faught finished second with 23 percent, enough to force Mullin into Tuesday’s runoff.

Wallace received 46 percent of the vote in the three-man Democratic primary in June compared to 42 percent for Herriman.

The heavily Democratic 2nd District spans eastern Oklahoma, from the Kansas border in the north to the Red River border with Texas in the south.

The winners of Tuesday’s runoffs will join independent Michael Fulks of Heavener on the Nov. 6 ballot.

Four Oklahoma Senate and four Oklahoma House runoffs also are on Tuesday’s ballot. Republicans currently hold a 32-16 advantage in the state Senate and a 67-31 edge in the House, with three seats vacant. The GOP is expected to maintain healthy majorities in both chambers, but Democrats are hoping to chip away at those advantages.