Whoever is the president next year may have the ability to appoint one or more justices to the US Supreme Court. But to get those justices confirmed, the president will need the US Senate behind him.
To gain Senate control from Republicans in November’s elections, Democrats will need a net gain of three seats (if former Vice President Joe Biden holds onto his lead over President Donald Trump and claims victory) or four seats (if Trump wins).
An early look at the data finds that Democrats are the slightest of favorites to take back the Senate. The chance Democrats net gain at least 3 seats is about 3-in-5 (60%), while the chance they net gain at least 4 seats is about 1-in-2 (50%).
There is still a lot of uncertainty. Democrats could realistically end up anywhere from a net loss of 4 seats to a net gain of 11 seats, though a few more times than not, they’ll end up in the majority.
To come up with these probabilities, I examined individual races in each cycle since 2006 and determined how well at this point state level polling (if available), incumbency, expert ratings, the past presidential results and the generic congressional ballot explained the ultimate result in each race. Then for any given cycle, I compared the total seats won vs. what the projections said at a given time.
The Democrats are doing fairly well not because they’re overwhelming favorites in any one or a select number of seats. Rather, it’s that they have a non-negligible to good chance in a lot of seats. Although Democrats only hold 12 of the 35 seats up, they have at least a 1-in-20 (5%) shot in 25 seats. Democrats almost certainly won’t win all of these seats, though it speaks to the large playing field.
Democratic chances have risen since I first looked at the map a year ago, in large part because the national environment continues to look good for them. They hold about an 8-point lead on the generic ballot. That’s about the same as it was in 2018, when it was 7 points, and about double what it was in 2016. Based on past trends, this large advantage suggests that races that may look like tossups right now are forecasted to move toward the Democrats over the course of the year.
And unlike in 2018, when Democrats were defending a lot of seats in states Trump won by significant margins, this year they’re only defending one (Alabama). That means they should be able to take advantage of a better national environment.
Right now, Democrats are clear favorites in three seats Republicans currently hold: Arizona (Sen. Martha McSally), Colorado (Sen. Cory Gardner) and Maine (Sen. Susan Collins). They’re favored to defeat incumbents between about 2-in-3 times (65%) to three in four times (75%) in these states. All three are in states that were decided by 5 points or less in the 2016 presidential election, and where the national environment is helping the Democrats. The limited polling in Arizona and Maine also point to Democrats being ahead by a small margin.
To counter those three seats, Republicans are heavily favored in Alabama. Democratic Sen. Doug Jones won a shocking victory in a 2017 special Senate election. The polling and strong Republican tilt of the state indicate that Republicans should win this race about 6-in-7 in seven times (85%).
If Democrats are going to net gain three seats while losing in Alabama, their best shot to get that additional pickup is in North Carolina. This is another state that was determined by less than 5 points in the 2016 presidential election, and where Republican Sen. Thom Tillis has actually been running slightly behind Democratic challenger Cal Cunningham in an average of polling. Cunningham wins a little bit north of half the time (55%), though it’s best to regard this one as a tossup.
Beyond these seats, Democrats have three seats where they are clear underdogs, though are far from out of it.
Republicans have about a 7-in-10 to 3-4 shot (70% to 75%) in Kansas, Iowa and Montana. Although Democrats aren’t likely to win any of these seats individually, their chance of winning any one of the three is higher.
Democratic chances in Kansas depend heavily on whether Republican Kris Kobach wins his party’s nomination. Kobach is deeply unpopular for a Republican in Kansas and lost the 2018 governor’s race. If Kobach is the nominee, Democrats could win their first Kansas Senate race since 1932. If Kobach doesn’t emerge as the Republican nominee, Democrats are likely out of luck.
Iowa is more an unknown. The polling is basically non-existent, though most analysts agree the race leans in Sen. Joni Ernst’s direction. Trump won the state by 9 points in 2016, but the national environment looks better for Democrats right now than back then.
Montana is all about whether Democratic Gov. Steve Bullock can transfer his popularity in a state Trump took by 20 points in 2016. The limited polling and the fact that Democrats won a Senate seat in 2018 suggests it’s possible. Republican Steve Daines, the incumbent, should still be regarded as the favorite, however.
After these seats, there are six Republican held seats where Democrats have a better than 1-in-20 (5%) chance: both Georgia races, Kentucky, Mississippi, South Carolina and Texas. There is a decent shot that at least one of these seats emerges as competitive down the line.
Michigan is the only Democratic seat not previously mentioned that has a better than 1-in-20 shot of switching parties. Sen. Gary Peters has about a 6-in-7 (85%) of beating back a challenge from Republican John James.
The lack of Republican pickup opportunities again point why Democrats have a real shot of wrestling control: Democrats simply have a wider playing field.
