Has there been a change in Senate-presidential vote correlation?

Shortly before the election, I wrote about the increasing correlation between Senate and presidential votes. 

In the wake of last month’s elections, where four Democratic Senate candidates prevailed in states Donald Trump won, some pundits are pronouncing an end to, or at least a respite for, that correlation. 

I think they misunderstand both the data and the mechanism. 

No doubt the precipitous decline in Senate mismatches — states where different parties won the presidential and Senate contests — is part of the evidence for the correlation. 

In 1986, 59 percent of Senate races were won by the party that lost the 1984 presidential contest in that state. That was the peak year for presidential/Senate mismatches, but through the late 1990s mismatches ran over 30 percent.  

Things changed in 2020 when just one Senate election produced a mismatch between the party of the Senate victor and the party the state’s presidential winner.  

2022 also yielded just a single mismatch.  

2024’s four mismatches seem to upend the pattern. However, the single mismatches in ’20 and ’22 are outliers.  

This year’s four mismatches translate into 12 percent, far less than the 59 percent record in 1986 or even the 30 percent we saw through most of the ’90s. 

More important, as I pointed out in the previous article, this phenomenon is not just about the binary of winning and losing. More subtly, it is about how close presidential and Senate candidates run. 

And that relationship is barely budging, and in some respects, is getting tighter.  

My Mellman Group colleague Edward Wu and I examined the difference between the Senate vote and presidential vote (or the previous presidential vote for a midterm) over Senate cycles. Since one third of the Senate stands for election every two years, over three two-year cycles, all 100 Senate seats face the voters. 

During the 1984-88 Senate cycle, on average, Democratic Senate candidates outperformed their presidential nominee by over 9 points. 

By the 2018-22 Senate cycle, that average difference had plunged to 1.6 percentage points.  

In 2024 alone, that average was a slightly lesser 1.3 percentage points, while in the 2022 Senate races taken alone, Democrats ran an average of 1.3 points behind Joe Biden in their states.   

The four Democrats who won in Trump states this year outperformed Harris by an average of less than 2.1 points.  

Of course, averages can obscure as well as illuminate.  

Looking at the data differently, from 2018 to 2022, 51 percent of Democratic Senate candidates ran within 3 points or less of their presidential candidate. In 2024, it was 73 percent.  

The Democrat who ran farthest ahead of Vice President Harris was Montana Sen. Jon Tester at 6.7 percent. In his previous race, Tester ran nearly 15 points ahead of Hillary Clinton’s 2016 mark. 

In Ohio Sen. Sherrod Brown’s last race, he posted a vote total 9.9 points higher than Hillary Clinton’s. This year, he bested Harris by just 3.7 points.  

Pennsylvania Sen. Bob Casey surpassed the presidential vote by a healthy 8.1 points in 2018, but only by eight tenths of a point this year.  

Wisconsin Sen. Tammy Baldwin eked out a win this year running just nine tenths of a point ahead of Harris. Six years ago, she outscored Clinton by 9 points. 

Nevada Sen. Jacky Rosen, another Democratic victor in a Trump state, garnered the same 2.5 points more than the presidential nominee in both 2018 and 2024. 

Sen. Bernie Sanders (I-Vt.) had no trouble being reelected in Vermont despite running behind Harris, albeit by one tenth of a point. But compare that to six years ago when he exceeded the presidential vote by over 15 points. 

To hear some pundits talk about this phenomenon one might conclude this correlation is causation — that the presidential vote acts as a barrier, preventing Senate candidates from doing better.  

However, the fact that Senate candidates and presidential aspirants run close to each other does not result from some magical hold candidates for chief executive exert over voters or from some gravitational pull emanating from the presidential vote. 

Rather, both candidates are running in a political environment characterized by partisanship and polarization, the combination of which locks voters into place.  

Whether they believe it or not, most voters are partisans. That identity as a Democrat or Republican does more to structure their attitudes toward candidates and issues than anything else. It puts the vast majority of voters in one camp or the other across most races.  

Polarization — the antipathy partisans exhibit toward the other party — holds them in place, making it difficult for one Democrat (or Republican) to outpace another by much.  

The unique qualities, backgrounds and messages candidates communicate to voters can still have electoral consequences, but they now matter less than the “D” or “R” next to their names.  

The data we’ve been exploring tell us that, except in extraordinary cases, party brands now matter more than personal brands.  

Mark Mellman is a pollster and president of The Mellman Group, a political consultancy. He is also president of Democratic Majority for Israel.

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