Everything You Need to Know about Roy Moore, Doug Jones, and the Alabama Senate Vote Tonight

Tonight, Alabamians will cast their ballots in what’s probably the most consequential election of the year for national politics. Republican Roy Moore and Democratic candidate Doug Jones are in a tight race for the Senate seat currently held by Luther Strange (who was appointed to replace Attorney General Jeff Sessions but lost the special election Republican primary to Moore). Republicans have had trouble getting some of their major policy initiatives through the Senate (e.g. repealing and replacing the Affordable Care Act), and a Jones win would make it more difficult for them to pass policy. Moreover, if Democrats want to retake the Senate in 2018, they need to defend all of their seats, and win three more seats. Arizona and Nevada are competitive, and Alabama could provide them with that third win.

This election is important, so here’s a quick, data-driven guide that’ll get you up to speed on the polls and some of the basics of Alabama politics.

What do the polls say?

There’s a lot of uncertainty in exactly where public opinion is on this race. RealClearPolitics gives Moore a 2.2 point lead, but that doesn’t guarantee a win. Polls can miss. In the Virginia gubernatorial election (about a month ago), Democrat Ralph Northam went into the race with a 3.3 point lead in the polling average and ended up with a 8.9 point lead—a 5.6 point error. In 2014, Senate polls overestimated Democratic candidates’ margin by four points on average and in 2012 they overestimated Republican Senate candidates’ eventual margin. For a more thorough overview of polling error and related issues, I’d recommend this piece, but the point is clear: Moore’s narrow edge in the polls could translate into a victory for either candidate.

Moreover, it’s hard to model the electorate in this race. Nobody knows exactly who is going to show up and vote in this election. Everyone in the world of elections analysis has emphasized this point, but pollster Mark Blumenthal of SurveyMonkeymight have demonstrated it most effectively. He applied various assumptions about turnout to his data and came up with wildly different results, ranging from an 8-point Jones win and to a 9-point Moore win. That, along with the differences between automatic and live caller polling, helps explains why the polls currently in the RCP average vary so widely, showing everything from a 9-point advantage for Moore to a 10-point edge for Jones.

There’s some evidence that Roy Moore has gained ground since the Washington Postinitially alleged that he had improper sexual contact with teenage girls while he was in his 30s. Moore gained ground in multiple polls after the Thanksgiving holidays, and some (thought not all) polls show him gaining ground since then. Emerson put Moore ahead by +3 in a late November poll, but they now have him ahead by +9. Change Research showed Moore’s lead growing earlier this month, though that seems to have leveled off in their final poll. Gravis and Strategy Research have also shown an increase in Moore’s lead since their last poll.