The upcoming midterm elections for Senate Democrats have been called “brutal” and “daunting” by the media. One reason given is that Democrats have to defend many more seats than Republicans do. That is indeed a good reason for thinking that Democrats will have a tough time making substantial gains in the Senate. There is another, not-so-good reason: 10 Senate Democrats will be running for re-election in states that Trump won. 2 of them, Senators Heitkamp and Manchin, are from states where Trump won by a margin of over 30 points. However, it has been very rare for Senators to lose re-election in circumstances that resemble the one these Democrats will be in in 2018.
Since 1982, there have been 60 cases that fit the following description:
- a Senator is running for re-election in a midterm year
- the Senator is from the party opposite the President
- the Senator’s state voted for the President in the prior election
Out of these 60 cases, only 3 (5%) resulted in loss.
Senator |
Year |
Democratic Minus Republican Margin |
Democratic Minus Republican Margin of State in Prior Presidential Election |
Max Cleland |
2002 |
-6.8 |
-11.69 |
Al D'Amato |
1998 |
10.5 |
28.86 |
Howard Cannon |
1982 |
-2.4 |
-35.65 |
Source: Wikipedia
In the 95% of cases where re-election was won, the average difference between the margin that the Senator won by and the margin that the Senator’s party lost by in the prior presidential election was about 40 percentage points. In other words, on average, these Senators improved on the performance of their party’s presidential candidate by an amount larger than the margin Trump won by in North Dakota and close to the one in West Virginia.
Senator |
Year |
Democratic Minus Republican Margin |
Democratic Minus Republican Margin of State in Prior Presidential election |
Difference |
Susan Collins |
2014 |
-37 |
15.29 |
52.29 |
Chuck Grassley |
2010 |
-31.3 |
9.54 |
40.84 |
Richard Burr |
2010 |
-12.1 |
0.32 |
12.42 |
Bill Nelson |
2006 |
22.2 |
-5.01 |
27.21 |
Ben Nelson |
2006 |
27.8 |
-33.22 |
61.02 |
Jeff Bingaman |
2006 |
41.3 |
-0.79 |
42.09 |
Kent Conrad |
2006 |
39.3 |
-27.36 |
66.66 |
Robert Byrd |
2006 |
30.7 |
-12.86 |
43.56 |
The rest of the data is here.
One reason that these Senators did so well is that the President’s party usually loses power during midterm elections. In the 21 midterm elections since 1934, the President’s party gained Senate seats in only 5.
Another reason is the incumbency advantage. Since World War II, incumbent Senators have won reelection about 80 percent of the time.
Red-state Senate Democrats may very well lose in 2018, but there is no reason at this time to think that it is likely that they will. While it is surely more difficult to win re-election in a solidly red state than a blue one, there are countervailing factors that make re-election easier.