UPDATE: Former Alabama Chief Justice and Republican Senate candidate Roy Moore rode a horse to the polls as he voted in the state's special Senate primary on Tuesday.
Moore wore a military T-shirt and black cowboy hat as he dismounted at the Gallant Volunteer Fire Department, where he votes in northeastern Alabama.
Moore jokingly looked shocked when a poll worker asked if he wanted to vote in the GOP or Democratic primary.
He then took only a few seconds to mark his ballot -- presumably for himself. Moore says it's odd to have only one race on a statewide ballot.
Moore is among a group of candidates for the seat previously held by Attorney General Jeff Sessions. He says riding a horse to vote is a family tradition.
___
ORIGINAL STORY: Polls have opened across Alabama as voters cast ballots in party primary elections for the U.S. Senate seat previously held by Attorney General Jeff Sessions.
Republican Sen. Luther Strange, who was appointed to fill the post temporarily, is seeking to fight off challengers that include former Alabama Chief Justice Roy Moore and U.S. Rep. Mo Brooks.
President Donald Trump has endorsed Strange and recorded automatic phone calls on his behalf.
Brooks has criticized Strange's backing by a super political action committee tied to Senate Majority Leader Mitch McConnell.
Democratic contenders include former U.S. attorney Doug Jones, environmentalist Michael Hansen and Navy veteran Robert Kennedy, Jr.
The primaries will go to a runoff unless a candidate gets more than 50 percent of the vote Tuesday.
Polls close at 8 p.m. EST.
This is a developing story.