When we launched our Senate forecast in September, Republicans had an approximately 53% chance of winning a majority in the Senate. That is now up to about 77%. The change hasn't come exactly linearly, though there certainly has been at least some trend line, specifically over the past month.
The GOP's chances rose slightly in early September and then fell again when a string of polls showed Democrats with surprisingly strong results. However, that high for Democrats didn't last long, and since the GOP's low of 53.9% on October 12th, they have steadily increased, almost daily, their chances of taking a majority in the next Congress.
In that time, what has changed? Not that much, actually. Most races have just shifted slightly to the Republicans, which has created an overall shift in our forecast.
In September, our two closest races were Iowa and Colorado. Those states are now both leaning towards Republicans. Now, the two closest races are Kansas and Alaska. Kansas was leaning Democratic about two months ago, and Alaska was leaning Republican.
Alaska, however, is the exception. The majority of races have shifted about 10 to 15% towards the Republican candidate. Below, we'll go into more depth on each race.
Beginning with the race Democrats are most likely to win, New Hampshire's Jeanne Shaheen has held on despite a surprisingly strong challenge from former Massachusetts Senator Scott Brown. The race has become tight over the past few weeks, but Shaheen still holds a polling edge. She is expected to win by about 2%, according to our forecast.
New Hampshire represents the only 'lean Democratic' state we have at this point, though North Carolina's Kay Hagan is nearly in that column. Her seat essentially must be won by Democrats in order for the party to have any hope of winning today. If Republicans were to win North Carolina, Democrats would only have about an 11% chance of winning, and that would include sweeping many states that they are clearly behind in at this point. Still, she has a 58% chance of winning tonight, and we project her to win by a margin of 1.2%.
Next in the tossup column is Kansas. Independent candidate Greg Orman could end up ruining the GOP's chances at a Senate takeover by turning what was once thought of as a safe Republican seat to a true tossup. He has about a 52% chance of winning at this point. The unknown factor is how the undecided voters in the race will vote. If they end up 'coming home' to the Republican candidate instead of largely splitting the vote between the two candidates, Roberts will end up winning. However, we assume Orman will win about 45% of the undecided vote, giving him a mere 0.3% win after it's all said and done.
Alaska is by far the state that could produce the biggest unknowns tonight. The polls won't be closed there until 1 am ET, and it could take weeks to tally all the mailed in and absentee votes. Polls (as expected) have been all over the place, with the average giving Mark Begich a very slight lead. But when factoring in the state fundamentals, Begich actually has less than 50% chance of winning (about 48%). That is essentially a coin flip. We project he will lose by about 1% to Dan Sullivan, but the uncertainty is high. Either candidate could win by about 5%, depending on which polls were closest.
Iowa and Colorado represent the first two 'leaning Republican' states. Polls have tightened in recent days in both states, but at this point, Democrats need to hope for a slight polling error or larger than expected turnout in order to keep either of these states.
Iowa's Joni Ernst has run a surprisingly strong campaign, while the Democrat, Bruce Braley, has made numerous unforced errors. The Democrat has only a 35% chance of winning now, down from about 50% in early September.
Meanwhile, the situation is nearly exactly the same in Colorado. The Republican, Cory Gardner, is running about 2 points ahead in the polls, but we expect that to tighten slightly on election day due to Colorado's mail-in ballot law, which we see as helping the Democrat slightly. In the end though, we expect Gardner to hold on to win by about 1.7%.
Georgia is a state in which the Republican Senator is retiring, leaving an open seat. Democrats are working to finally turn Georgia purple, and it shows. Michelle Nunn is trailing by about three points currently, which is within the margin of error of most polls. We project that this race will go to a runoff, however, as the winner will need to win by more than 50% of the vote. We currently expect David Perdue to get just short of that, 49.9%. At this point, Nunn should be hoping for a runoff, because there is only about a 5% chance she could win outright tonight, given the current polling.
Louisiana's Mary Landrieu is in much the same boat, although she is most certainly not hoping for a runoff. We expect her to 'win' with about 46.4%, well short of the 50% she also needs for a runoff. Her problem, however, is that the vast majority of the votes not going to her main opponent, Bill Cassidy, are going to an even more conservative opponent. It's unlikely she will pick up many of those voters in a runoff, and her chances of winning eventually are only 14%.
The next three races look to be safe for Republicans. It would require a huge polling error in any of these states to give an upset for the Democrats. Arkansas' Mark Pryor was running neck and neck with his Republican opponent for much of the spring and summer, but since then, Cotton has pulled ahead in the polls, and we expect him to win by about 6.2%.
There is a similar dynamic in Kentucky, home of Senate Minority Leader Mitch McConnell. His Democratic opponent was keeping the race close until a couple weeks ago, when she infamously refused to say who she voted for in the last Presidential election. Now, McConnell has pulled ahead, seemingly taking all of the previously undecided voters with him. He is favored to win by 7.8%.
And finally, Republicans had a bit of a scare in early October when a couple polls showed their candidate, Mike Rounds, with only a slim lead against either the Democratic or Independent candidates. However, after more polls were released and money was poured in the state to help shore him up, it seems like Rounds will safely win, with about 47% of the vote.
So, what does this all translate to? We now expect Republicans to net five seats tomorrow night, bringing them to 50 seats and leaving the Democrats with 48 seats (including Greg Orman). This scenario would require that both Michelle Nunn and Mary Landrieu would need to win their runoff elections, an extremely unlikely scenario. If Republicans win both, they will hold 52 seats (not including Orman) in January.
Democrats at this point need to hope for the polling to be slightly wrong in two of the three states including Alaska, Colorado, and Iowa. It's not an impossible scenario, and there's about a 25% chance Democrats could pull off an upset in those states, which is, not coincidentally, about the same chance they currently have at keeping the Senate in our overall forecast.
Either way, we won't know for sure who will control the Senate likely until January. It's going to be a fun and crazy night.