OKLAHOMA CITY - Oklahoma election officials say nearly twice as many Republicans and Democrats are voting early in this year's primary elections compared to four years ago, and enthusiasm is particularly high among Democrats.

Oklahoma Election Board Secretary Paul Ziriax (ZEER'-iks) said nearly 31,000 registered Democrats voted early ahead of Tuesday's elections, more than twice the 14,100 who voted early in 2014.

Turnout is sharply higher for Republicans, too. Ziriax says about 36,600 Republicans voted early this year, compared to about 21,600 in 2014.

Oklahoma's open governor's seat, a state question on medical marijuana and a record number of candidates running for state House and Senate seats all are expected to drive turnout Tuesday.

Polls are open from 7 a.m. to 7 p.m. across Oklahoma.