Thought you were done with election season? Not so fast. On Tuesday in Mississippi, the final U.S. senator of the 116th Congress will be chosen, determining whether Republicans have 52 or 53 seats come January. It’s the second round of voting in the special election that was scheduled after Republican Sen. Thad Cochran resigned in April. We’re not forecasting this runoff, but nonpartisan handicappers rate the Republican as the favorite. Catch up on everything you need to know about the election below, then join us back here on Tuesday night for our live blog.

1. The players

Although the special election is nominally nonpartisan, the battle lines are clear. The Republican candidate is incumbent Sen. Cindy Hyde-Smith, the former state agriculture and commerce commissioner who was appointed to Cochran’s seat in March. The Democratic candidate is Mike Espy, former President Bill Clinton’s secretary of agriculture and a former six-year congressman from Mississippi.

National Republicans have mobilized on behalf of Hyde-Smith in recent weeks, though it’s not clear if they are genuinely concerned or simply taking no chances. President Trump is hosting not one, but two rallies for her on Monday, and the National Republican Senatorial Committee and Senate Leadership Fund are reportedly spending more than $1 million each on ads. Democrats have responded in kind, if not proportionally: Sens. Cory Booker and Kamala Harris have stumped for Espy, and the liberal Senate Majority PAC has made a $500,000 TV buy.

But both candidates have baggage. Republicans have focused their ads on Espy’s 1997 indictment for accepting improper gifts when he worked in the Clinton administration (although he was acquitted on all counts in 1998) and his more recent lobbying work for a dictator accused of crimes against humanity. And Hyde-Smith has come under fire for a series of controversies, mostly about her relationship with Mississippi’s Confederate and Jim Crow past. Most notably, she praised a close supporter by saying, “If he invited me to a public hanging, I’d be on the front row.” Many saw racial undertones to the quip given that Espy is black and that Mississippi has a long history of lynchings. As a result, corporations like Walmart and Major League Baseball have asked for refunds of their donations to Hyde-Smith’s campaign, but it is far from certain how much the controversies will matter to Hyde-Smith’s (mostly white) Mississippi base.

2. The partisanship

The first round of voting on Nov. 6 was a jungle primary in which all candidates, regardless of party, appeared on the ballot. Hyde-Smith finished first with 41.3 percent, followed by Espy at 40.9 percent. A second Republican candidate, state Sen. Chris McDaniel, received 16.4 percent, and a second Democrat, former intelligence officer Tobey Bartee, received 1.5 percent. The race is now headed to a runoff between the top two finishers because no candidate got over 50 percent of the vote.

The near-tie in Round 1 might make the runoff look like anyone’s ballgame, but it’s not. It’s pretty easy for a Democrat to crest 40 percent of the vote in Mississippi — it’s happened in each of the last three presidential elections. That’s because Mississippi has a higher percentage of black residents than any other state — more than 36 percent of the citizen voting age population — and they vote strongly Democratic. But it’s much harder for a Democrat to get those extra 10 points to reach a majority, because the state’s white voters are almost as strongly Republican, and there are relatively few swing voters. Thus, Mississippi is one of the least elastic states in the country — in other words, a perennial 60-40 red state, just like it was in the first round of the special Senate election (in aggregate, Republican candidates got 57.7 percent and Democratic candidates got 42.3 percent).

So Espy is probably pinning his hopes on the possibility that the Nov. 27 electorate looks different from the Nov. 6 electorate. Indeed, it seems as if he is specifically trying to translate Hyde-Smith’s “public hanging” comment into outsized African-American turnout on Tuesday. That would be a shift from the first round, when voter turnout in the state didn’t disproportionately lean Democratic — the 15.6-point aggregate Republican lead from Nov. 6 practically matched Mississippi’s FiveThirtyEight partisan lean of R+15.4. But an irregularly timed special election like Tuesday’s is susceptible to weirder turnout scenarios whereby one party could vastly outnumber the other because of an enthusiasm gap. For example, maybe Republicans who voted for McDaniel on Nov. 6 won’t turn out for Hyde-Smith in the same numbers. If that happens, it would fit in with a trend of Democratic overperformance in other oddly timed special elections in 2017-2018, in which Democrats outperformed their constituencies’ base partisanship by an average of 16 percentage points. That type of overperformance would give Espy a chance.

However, there are plenty of reasons to think that won’t happen too. Maybe Democratic enthusiasm has been defused now that the party has succeeded at flipping the House. Or maybe Mississippi’s inelasticity will just prevent Democratic overperformance from reaching those lofty heights.

3. The polling

Indeed, November’s only public poll of the runoff suggests that Espy will outperform the average Democrat, but not by enough to win. A survey conducted between Nov. 19 and 24 found Hyde-Smith leading Espy 54 percent to 44 percent; the poll was sponsored by a Republican-leaning blog but jointly conducted by one Democratic and one Republican pollster. The most recent independent poll was conducted by Marist College in mid-October, back when the runoff was purely hypothetical; it found Hyde-Smith leading Espy 50 percent to 36 percent. So it’s possible that the race has narrowed in the past month, but probably not by enough to matter. The New York Times did report on a private Republican poll that purportedly showed Espy coming within 5 points of Hyde-Smith in mid-November, but we are always leery of trusting internal polls.

In the end, there’s not a lot of evidence that Hyde-Smith’s gaffes have thrown this race wide open. (Comparisons to Roy Moore in next-door Alabama seem overblown; it took a scandal of epic proportions to throw that special election to Democrats.) On the other hand, there is a lot of evidence that Mississippi is an intractably red state. We’ll find out for sure on Tuesday night; polls close at 8 p.m. Eastern.