In the run-up to Election Day, we wondered whether more voters than normal would split their tickets because of Donald Trump’s unique candidacy, perhaps voting for Republicans down-ballot but for Hillary Clinton in the presidential contest. Republican Senate candidates, unsure of how to deal with Trump, tried different approaches — endorsing him, disavowing him, refusing to say whom they’d vote for. In the end, it didn’t matter. Every state that elected a Republican candidate for Senate voted for Trump, and every state that elected a Democratic Senate candidate voted for Clinton.
The 2016 Senate elections were the most nationalized ever.
The amount of straight-ticket voting was unusual even for the highly polarized era we live in. Four years ago, for example, Democratic Senate candidates won in some states where President Obama lost by healthy margins, including Indiana, Missouri and North Dakota. Republicans, meanwhile, held their seat in Nevada even though Mitt Romney lost there by 7 percentage points.
Nothing like that happened this year. Instead, one of the clearest trends in recent American politics — growing polarization and partisanship — accelerated. Most voters have sorted themselves into two camps: liberal Democrats and conservative Republicans. This trend is apparent up and down the ballot to a degree that we’ve never seen before.
Indeed, this is the first time that all the states (with Senate races on the ballot) have voted for the same party in both the presidential and Senate races. Senators were first popularly elected in 1914, and the next presidential election took place two years later, in 1916. So that’s 100 years and 26 presidential election cycles in all. You’d have to go back to 1920 to come even close to seeing anything like it. In that election, the only state that didn’t vote for the same party in the presidential and Senate race was Kentucky. It chose Republican Richard Ernst for Senate by less than 1 percentage point and Democrat James Cox for president, also by less than 1 point.
But it’s not just the binary win-loss statistics this year that stand out as unique. It’s how close the presidential and Senate votes were within states. Consider the 11 states that we identified as “states to watch” in our Senate forecast, plus Colorado and Louisiana1:
| REPUBLICAN MARGIN | ||||
|---|---|---|---|---|
| STATE | SENATE | PRESIDENTIAL | DIFFERENCE | ABS. DIFFERENCE |
| Nevada | -2.4 | -2.4 | 0.0 | 0.0 |
| New Hampshire | -0.1 | -0.3 | +0.2 | 0.2 |
| Pennsylvania | +1.7 | +1.2 | +0.5 | 0.5 |
| Colorado | -3.7 | -2.8 | -0.9 | 0.9 |
| Illinois | -14.2 | -16.0 | +1.8 | 1.8 |
| North Carolina | +5.8 | +3.8 | +2.0 | 2.0 |
| Wisconsin | +3.4 | +1.0 | +2.4 | 2.4 |
| Louisiana | +25.2 | +19.7 | +5.5 | 5.5 |
| Florida | +7.7 | +1.3 | +6.4 | 6.4 |
| Arizona | +12.1 | +4.3 | +7.8 | 7.8 |
| Indiana | +9.7 | +19.3 | -9.6 | 9.6 |
| Ohio | +21.4 | +8.6 | +12.8 | 12.8 |
| Missouri | +3.2 | +19.1 | -15.9 | 15.9 |
| Average | +1.0 | 5.1 | ||
Republican Senate candidates generally outperformed Trump, but the average difference between the Republican Senate candidate’s margin and Trump’s margin was just 1 percentage point. Trump wasn’t much of an albatross for down-ballot Republicans. There were some outliers, however. Republican Roy Blunt ran well behind Trump in Missouri, for example, and Republican Rob Portman ran well ahead of him in Ohio. So candidates can still make a difference, although below we show that their influence is reduced compared with previous eras. Still, in a majority of these races, the difference between Trump’s margin and the Republican Senate candidate’s margin was less than 3 percentage points.
Meanwhile, voters didn’t seem to care whether their Republican candidate endorsed Trump or not. The three races in which Republican Senate candidates seemed to struggle most with how to deal with Trump (Nevada, New Hampshire and Pennsylvania) were among those with the lowest level of split-ticket voting. Trump and Republican Joe Heck lost by a small margin in Nevada. Trump and Republican Kelly Ayotte barely lost in New Hampshire. Trump and Republican Pat Toomey barely won in Pennsylvania.
Here’s another way to look at how little ticket-splitting there was. For each Senate race, I compared the final vote share margin with a version of the Cook Political Report’s partisan voter index,2 a measure of each state’s presidential preferences over the past two election cycles. I did the same thing for Senate elections going back to 1982.
Again, what we see here is a modern record. As of Thursday, a ridiculously high 83 percent of the Senate margins can be explained3 by the weighted Cook PVI. That’s 7 percentage points higher than it was in 2014, which itself was a record. From 1982 through 2008, there was only one election in which more than 40 percent of the Senate margins across the states were explained by the presidential vote. If you want to know how a state will vote in a Senate race, looking to how it voted in the previous two presidential elections tells you almost everything you need to know. And this phenomenon is relatively new and coming on very strongly.
If this pattern continues in the next couple of election cycles, it’ll be very bad news for Democrats. Every state has the same number of senators regardless of population, and there are more Republican-leaning states than Democratic-leaning states in presidential elections right now. Trump won 30 states, even as he lost the popular vote.
Given that politics is mostly cyclical (i.e., the national electorate favors Democrats and Republicans equally over time), the current makeup of the parties’ coalitions means that over the long term, Republicans are in a far better position to win Senate seats than Democrats are. For Democrats’ position to improve, they need to change their coalition, or voters need to start splitting their presidential and Senate tickets again. Otherwise, the Democrats will need to get used to being locked out of power.