It's been a few months since we last released our Senate forecast. Despite being closer to the election and a plethora of new polls, we are still no closer to knowing who will control the Senate in 2015. In fact, since the last update, the result has become even more uncertain. In April, Battleground270 forecast that the GOP had a 57% chance of taking control of the Senate. The model was not updated in July or August, but had it been, it would have shown an even greater advantage for the GOP as their candidates were polling much better.
Despite the increased uncertainty of which party will control the Senate, there is now less uncertainty in the majority of individual races. Because we are now closer to election day, more weight is put on current polling in the model for determining the win likelihood for each candidate. For instance, a average 4 pt polling lead for a candidate in April would result in a less robust win likelihood than a 4 pt polling lead only 45 days out from the election.
In fact, the battle to control the Senate has come down, more or less, to only two races. In April, Battleground270 applied the 'tossup' category to five races: Alaska, Georgia, Kentucky, Michigan, and North Carolina. Since then, all five of those races have broken towards one side or the other. The first three are now 'leaning' or 'likely' GOP wins while the final two are the same for Democratic wins.
Now, the only two races rated as tossups are Colorado and Iowa. We'll go more into depth on the individual races in a moment. Below is the familiar graph depicting the 'win likelihood' for Democrats for a certain number of seats.
As it stands, the most likely scenario is that Democrats will be just short of the majority with only 49 seats; there is a 24.8% chance of this occurring. However, there is a 23.7% chance of Democrats keeping 50 seats and therefore keeping the Senate. In total, the GOP has a 52.8% chance of taking control of the Senate, down from 57% in April.
Now, let's look at what has changed. Only one seat has been added into the "Safe Democratic" rating, and that's Virginia Senator Mark Warner. Despite Gillespie jumping into the race to challenge Warner, the incumbent Senator has held consistently strong polling leads and is now a sure win for Democrats.
There are still only two states in the "Likely Democratic" column. Senator Shaheen has improved her chances of winning since April, despite her lead in the polls narrowing a bit. This is due to the fact that she still maintains a lead in the mid-to-high single digits with only 45 days to go in the campaign.
Michigan's Senate race, however, has gone from a pure tossup to being likely won by the Democratic candidate, Gary Peters. Peters began the race as an underdog to the GOP candidate, Terri Lynn Rand. However, as the year went on, the traditionally more Democratic state has shifted to give Peters strong polling leads against his GOP rival. The Republican party has now essentially written off Michigan as a pickup opportunity.
Meanwhile, the "Leans Democratic" category is seeing some new faces, the most surprising of which is Kansas Senator Pat Roberts. In April, we gave Roberts a 99% chance of winning his re-election. Many things have happened since, however. First and foremost, Roberts had to fight a bloody primary against a Tea Party challenger. The primary weakened the incumbent, but the real story is the entrance of a third party independent candidate named Greg Orman and the exit of the Democratic candidate, Chad Taylor.
Orman is currently leading Roberts in the polls by mid-to-high single digits, and the only reasons this isn't a "likely" Democratic pickup is because Kansas is still a very conservative state and Orman has not declared which party he will caucus with in the Senate. Most believe he would side with the Democrats, but because there is some uncertainty, the model puts him in the "Leans Democratic" category.
Also now in that category is North Carolina Senator Kay Hagan. For the past year or so, Hagan and her GOP challenger have been roughly tied in the polls; until now. Beginning in early September, Senator Hagan has begun to break away from Tillis to open up an approximate 4 pt polling lead. Should she keep this lead going into election day, she will be a heavy favorite to win.
The two races rated as a tossup were both previously leaning democratic. In both cases, polling has gone back and forth between modest leads for the Democrats and small leads for the Republicans. However, with only just over a month to go, numerous polls are showing a dead heat in these two states. Republicans would likely need to win at least one of these states in order to win the Senate. This is due to the fact, stated above, that the race in Kansas is leaning towards Democrats, so the GOP must pick up an extra seat to make up for that.
Democrats' chances of winning have deteriorated in Alaska and Georgia, but have risen slightly in Arkansas. In general, Democrats are not polling terribly in any of these states. Alaska's Mark Begich is running relatively even with his opponent, Dan Sullivan. However, the model takes into account state voting histories, and Alaska's is extremely conservative. If Begich's polling remains stable throughout October, his chances of winning will increase, but he will likely need to be running ahead of Sullivan on election day to see a victory at the ballot box.
Arkansas' Mark Pryor was always thought of as the most vulnerable Democrat, but that title now probably goes to Louisiana's Mary Landrieu. Pryor has run a remarkably good campaign and is only running a few points behind his opponent, Tom Cotton, despite the heavy Republican lean in the state. However, like Begich, Pryor will need to be running a bit ahead on election day if he hopes to survive.
Finally, in Georgia, Democrats' hope of a pickup opportunity is slowly fading. Republicans chose businessman David Perdue as their nominee, and since the primary, Democrat Michelle Nunn has been slightly behind in the polls. A gaffe or stronger than expected turnout are what's going to be needed to bring Nunn's campaign a victory.
As I mentioned above, Louisiana Senator Mary Landrieu is now the most imperiled Democratic incumbent. Her largest obstacle to victory is not winning on November 4th, but winning the expected runoff on December 6th. Because of Louisiana's election laws, no candidate will likely win on the 4th, pushing the top two contenders into a runoff the following month. In all recent polling, Landrieu is behind her expected GOP runoff challenger, Rep. Bill Cassidy. If the GOP don't pick up enough seats in November, expect both parties to spend heavily to win the runoff.
In Kentucky, Republican Senate Minority Leader Mitch McConnell is maintaining a modest, yet stubborn lead against Democratic Secretary of State Alison Lundergan Grimes. While McConnell is deeply unpopular in his home state, the political climate may just prove too steep of a climb for Grimes, especially in a state as conservative as Kentucky. Unfortunately, there haven't been any new polls for a couple weeks, so look for this race to be updated soon when fresh polls arrive.
Finally, we arrive at our "Safe Republican" list. With the exception of adding Montana and subtracting Kansas, this list has remained the same. Some will note that under Alabama's row, Sessions now has a 0% chance of losing. This is because he is uncontested.
In summary, the race for the Senate is as close as ever, but there are fewer states that now "matter". That could change within the next month and a half, but in general, as we get closer to election day, more outcomes will drift towards being certainties and away from the possibility of being a tossup.
From this point forward, I plan on updating the Senate forecast regularly to reflect changes in the day's polling and news. I will give a short description of what has changed, if anything.