Republican candidates in the Alabama Senate primary are facing off Tuesday in the special election for the remaining term of former Sen. Jeff Sessions.

If none of the nine candidates garner more than 50 percent of the vote, the top two contenders will head to a Sept. 26 runoff. The top three candidates who have been polling ahead of the rest of the field are the incumbent Sen. Luther Strange, who was appointed to the seat in February after Sessions resigned to become attorney general; Roy Moore, the former Alabama Supreme Court chief justice; and Rep. Mo Brooks of the 5th District.

Seven Democrats are facing off in their own primary Tuesday but whoever wins the Republican contest will be in a strong position to win the general election on Dec. 12. Inside Elections with Nathan L. Gonzales rates this race Solid Republican. 

Here are three things to watch as the results come in Tuesday night: 

1. Margin

Recent polls suggest Moore could finish ahead of the pack. A Cygnal poll released last week showed nearly 31 percent of those surveyed backed Moore, while nearly 23 percent supported Strange and 18 percent favored Brooks. Roughly 13 percent remained undecided. 

The margin would signal where voters stand heading into the runoff. If Brooks does come in third, his supporters could swing to Moore, as both have cast themselves as anti-establishment conservatives. But Strange’s campaign would likely try to win their support by highlighting President Donal Trump’s endorsement of the appointed incumbent.

If Strange is able to narrow the gap with Moore, it could be an indication that Trump helped push his supporters in Strange’s direction through his endorsement. Such an overperforming of recent polls could also show whether the money backing Strange has made a difference.

A super PAC aligned with Senate Majority Leader Mitch McConnell has spent roughly $4 million on the race, and could spend an additional $4 million on the runoff. The group, known as the Senate leadership fund, targeted Brooks in most of its negative ads, but the fund recently shifted its focus entirely to Moore.

2. Turnout 

Alabama officials are expecting a low turnout of 20 percent to 25 percent, about 10 points lower than other primary elections. Some GOP strategists say one impact of Trump’s endorsement could be the mobilizing of Trump supporters who were undecided, or not planning to turn out.

Groups supporting Strange have made a last-minute push to mobilize voters. America First Action, a super PAC aligned with Trump, announced Friday it would spend between $150,000 to $200,000 on digital ads targeting the president’s supporters. And the National Republican Senatorial Committee’s independent expenditure arm disclosed it would spend an additional $200,000 in the final days before the primary, likely for get-out-the-vote efforts. Trump also recorded a robocall to voters Monday, encouraging them to go to the polls and vote for Strange.

3. Third-place finisher

The third place finisher who does not make the runoff will also be one to watch. If Brooks misses out on the top two spots, he has said he would seek re-election to his House seat. Clayton Hinchman, an Army veteran who lost his leg serving in Iraq, is currently running in the GOP primary for the 5th District seat. Brooks said in a recent interview in Alabama he was focused on the Senate race and was not necessarily worried about his House race. 

“In one sense, I worry about all of them, but in another sense, I know from past history that no opponent has ever done better than lose by 30 points,” Brooks said. “And so that gives me some degree of comfort as to what is likely to be the outcome in 2018 if we are surprisingly not able to win this Senate seat.”

If Strange does not make the runoff, he essentially becomes a lame-duck senator, set to leave after the Dec. 12 general election. His loss would also raise questions about the effectiveness of outside spending and the impact of opponents tying Strange to McConnell.

Moore’s loss would come as a surprise since he’s been leading in recent polls, but it would raise questions about whether he would continue to run for office. He was suspended from the state Supreme Court in 2016 after he told state probate judges to refuse to issue same-sex marriage licenses and he recently lost an appeal. Moore resigned from the bench in April when he announced his Senate bid.

“I don’t feel like I’m finished working for government and for good government,” Moore said in a recent interview explaining his decision to run for Senate. But a loss would raise questions about his political future.