The two men, who represent different factions within the Alabama Republican Party, will face off in a Sept. 26 runoff after neither captured more than 50 percent of the vote.
Strange was forced into a runoff with the firebrand jurist despite an endorsement from President Donald Trump and heavy investment by a super political action committee tied to Senate Majority Leader Mitch McConnell. The winner will face Democratic nominee Doug Jones in a December election
Moore, who was twice removed from his duties as chief justice for his stances supporting the public display of the Ten Commandments and against gay marriage. Moore expressed optimism Tuesday after a horseback ride to his polling place, an election day tradition of his.
"We look forward to registering our vote to make this country great again, to make it good again. And we're looking forward to voting and hope we have a good turnout today, because I know there's a lot of motivation out there to change Washington," Moore said.
Strange had emphasized his Trump endorsement but had acknowledged all along that a runoff was likely because of the crowded GOP field.
"The final pitch is: Listen to President Trump. The key is someone who will support him in Washington. He's endorsed me," Strange said Monday as he encouraged Alabamians to get out and vote.
Trump's approval rating has hit a new low of 34 percent, according to Gallup, but strong currents of support still flow through the Republican electorate in Alabama, where the GOP candidates went all-out to attract Trump voters and throw shade on the Washington, D.C. "swamp."
Trump recorded a Monday night robocall urging voters to choose Strange. Strange's campaign quickly pushed the message out in robocalls to try to get voters to the polls in the late summer special election. The primary had low turnout which would favor candidates like Moore, who has a heavy following among the state's evangelical voters but has alienated others with his hardline religious right stances.
Voting was steady at St. James Methodist Church on the outskirts of Montgomery, where retired teacher Tommy Goggans said he turned out specifically "to keep Roy Moore from getting it." Why? "He's been kicked out of everything he's done."
In the rural community of Gallant in northeast Alabama, Jimmy Wright, 41, showed up early Tuesday to vote for Moore.
Aside from being a neighbor, Wright said, he likes the way the ousted judge conducted his campaign.
"He's the only one who hasn't been talking crap about the others," Wright said. Trump's support for Strange didn't matter to him, he said.
GOP challenger U.S. Rep. Mo Brooks, who finished third, had hammered at Strange's support from McConnell, asking voters to send a message that "our Alabama Senate seat cannot be bought by special interests in Washington D.C."
"Alabama has a chance to send a message, a huge message -- not only to Washington D.C. -- but the United States of America. We can send a message that we are tired of this do-nothing Senate," Brooks said.
Strange was Alabama's attorney general before he was appointed to the Senate in February by Gov. Robert Bentley, who soon resigned in scandal. Strange said he did Bentley no favors, but his challengers questioned the ethics of seeking the appointment while investigating the governor.
On the Democratic side, a former U.S. attorney under the Clinton administration, Jones was backed by former Vice President Joe Biden and some other national party figures. He is perhaps best known for leading the prosecution of two Klansmen for the 1963 bombing of a Birmingham church that killed four little girls.
Although Alabama has not been represented by a Democrat in the U.S. Senate in 20 years, Jones has said Democrats must not concede the seat without a fight. He says Democrats can win if they can turn the conversation to "kitchen table issues" such as wages, health care and jobs.