The presidential election is sucking up everyone’s attention, but make no mistake: Control of the next United States Senate remains very much in doubt.
Democrats currently have a 57 percent chance of winning a Senate majority according to our polls-plus forecast and a 56 percent chance in polls-only. Those numbers have been fairly consistent since the conventions. In our polls-plus forecast, for instance, Democratic chances have never dropped below 52 percent and have never risen above 73 percent.1
To control the Senate, the Democrats need a net gain of four seats (they hold 46 seats now) if Hillary Clinton wins the presidency or five seats if Donald Trump wins. Right now, they have at least a 75 percent chance of winning currently Republican seats in Illinois and Wisconsin. The bigger question is whether they can win any three of the following seven seats: Florida, Indiana, Missouri, Nevada, New Hampshire, North Carolina and Pennsylvania.
Sen. Marco Rubio has a decent lead in Florida — a shade over 4 percentage points in our polls-plus forecast. But those other six states feature super close races, and — not coincidentally — all seven top our tipping-point rankings, which measure each state’s chances of deciding Senate control. With the exception of Missouri, where we haven’t had a poll since mid-September, polls released over the past week haven’t consistently shown a clear advantage for any candidate in those six tight races. Here, for example, are all the Senate polls we’ve gotten since Monday:
When you put all the polls together, no candidate leads by more than 3 percentage points in these six states, according to our polls-plus forecast. Democrats hold a small advantage in Indiana, New Hampshire and Pennsylvania, while Republicans retain a slight edge in Missouri, Nevada and North Carolina.2 In five of these races,3 at least one poll released since the beginning of September shows the Democratic candidate ahead and at least one shows the Republican candidate ahead. No candidate has better than 2-to-1 odds in any of these races, according to our polls-plus forecast.
Of course, it’s possible we’ll wake up on Nov. 9 and find that one party swept all these close races. That has happened before, including in 2014, when Republicans beat their polls in virtually every battleground state. So if there is a polling error in one of these states, we’d be more likely to expect an error in that direction across the board. It’s quite possible, therefore, that Democrats will win all six of these tight races plus the two in which they have significant leads and end up with a net gain of seven seats.4 Indeed, about 20 percent of the time in our polls-plus simulations, Democrats net a gain of at least seven seats in the Senate. The reverse is also possible; we have Democrats netting two seats or fewer nearly 25 percent of the time.
This year, however, could be different. If you look at the races where the polls are really close, the states that are up for grabs are pretty dissimilar. You have a New England state in New Hampshire, a Mid-Atlantic state in Pennsylvania, a Rust Belt state in Indiana, a Southern state in North Carolina, a sort-of-Midwestern state in Missouri, and a western state in Nevada. You have a state with a lot of black voters in North Carolina, a state with a lot of Latino voters in Nevada, and a state with a lot of white voters in New Hampshire. Of this group of states, New Hampshire is the whitest (which helps the Republican), but its white voters are the most likely to have a college degree (which helps the Democrat). Nevada is the most diverse state, but its white voters are the least least likely to have a degree. And white voters with and without a college degree are voting very differently at the top of the ticket. The point is that we shouldn’t necessarily expect these states to move together in the final month of the campaign.
For now, the safest thing to say is that the race for the Senate remains tight. Democrats hold a slight advantage, but it’s only slight.