Washington(CNN) Sen. Luther Strange and Roy Moore have one final day of campaigning before Republican voters in Alabama will take to the polls in a GOP primary to decide who they want to run against Democrat Doug Jones in the special election to fill a US Senate seat.
Strange, who was appointed by then-Gov. Robert Bentley to finish out the term after Jeff Sessions became attorney general, is running against Moore, the former chief justice of the Alabama Supreme Court in the GOP primary.
Strange is seen as an establishment Republican who has strong support from President Donald Trump and Senate Majority Leader Mitch McConnell to keep the seat, which Sessions had held for two decades. He has been propped up by more than $9 million in spending from the Senate Leadership Fund, a super PAC aligned with McConnell.
Trump boosted Strange on Twitter Tuesday morning: "Luther Strange has been shooting up in the Alabama polls since my endorsement. Finish the job - vote today for 'Big Luther.'"
Meanwhile Moore, a hardline conservative Christian, has cast the campaign as an opportunity to reject McConnell -- a much less popular figure among Alabama Republicans than Trump. He has the support of Steve Bannon, the recently ousted former White House chief strategist, and former Alaska Gov. Sarah Palin.
It's Pence vs. Bannon in final day of Alabama Senate race
Moore is no stranger to controversial remarks -- he is well-known for a history of bombastic statements about race, sexual orientation and more.
The 70-year-old was ousted from his state Supreme Court job twice -- first in 2003 for refusing to remove a monument of the Ten Commandments at a state court building then again in 2016 for refusing to abide by the US Supreme Court's ruling legalizing same-sex marriage nationwide.
In 2014, Moore wrote letters to all 50 state governors calling on them to convene a constitutional convention to ban same-sex marriage.
While some of his views have been widely condemned in the US media, his views align with many voters in Alabama. He has a definite brand and is somebody who has been well-known in the state for decades.
Whoever wins the primary will advance to the December 12 special election to face Jones -- who has the backing of former Vice President Joe Biden. Biden is planning to visit Alabama on October 3 to campaign with Jones.
A primary win by Moore would open Alabama's US Senate seat to Democrats, Trump told radio-hosts "Rick and Bubba" Monday morning.
"Luther Strange is going to be a great senator," Trump said. "He loves Alabama, he loves the states and he loves the country. He will absolutely win against the Democrat. Ray (sic) will have a hard time. If Luther wins, the Democrats will hardly fight. If Ray wins (Democrats) will pour in $30 million."
Republicans are closely watching Alabama for signs of what could happen in other races featuring anti-establishment challengers next year.
In Nevada, Republican Sen. Dean Heller already faces a primary fight against Danny Tarkanian. In Arizona, Sen. Jeff Flake faces conservative Kelli Ward. Both, like Moore, have Bannon's support.
Polls close Tuesday in Alabama at 7 p.m. local time, 8 p.m. ET.