But at least one key indicator suggests Trump is, indeed, doing worse than the average Republican would be doing in the same conditions — Trump doesn’t seem to be receiving the average boost an incumbent does compared to his party brethren in the House.
The fact that Biden’s lead is wider than the House Democrats’ edge is unusual. If it holds, it would be ahistoric.
You’d expect that Trump would be doing better than Republicans running in the House. The simple reason is that more Democrats (i.e. the majority party) have an incumbency advantage in the House, while Trump enjoys that same advantage for the presidency.
Since 1940, there have been eight elections where an incumbent president was running for another term and his party did not control the House. In these elections, the president has done better than the members of his party running for the House six of eight times (75%). The president has never underperformed his House counterparts by more than 3 points in any of these years.
Of course, eight elections is not a particularly large set of elections. We can widen it out to include the elections where the incumbent president was not running for another term. In these cases, we should still expect the party that controls the majority in the House to do better in House races than it does in the presidential race because incumbents do better.
If we include these elections in our group, the party with House control has outrun their party’s presidential candidate 13 of 15 times (87%) in the last 80 years.
Or put another way, the minority party in the House has done better in the presidential race 13 of 15 times when they either control the White House or the incumbent president is not running for re-election. The vast majority of the time, it’s not even close.
In elections where the House minority either controls the White House or an incumbent is not running for re-election, the House minority party has done better in the presidential race by 3 points or more (rounded) 12 of 15 times (80%) in the last 80 years. Trump right now is 5 points below this threshold, as he is underperforming House Republicans by 2 points.
Interestingly, the generic congressional ballot has remained fairly steady for most of 2020. Trump was doing better than House Republicans for much of the year, until this summer.
This suggests that Trump was hurt by probably two issues: his handling of the coronavirus pandemic and race relations. The coronavirus pandemic has gotten worse this summer, while race relations were brought to the news late this spring after the killing of George Floyd.
Perhaps the good news for Trump is that if he is doing worse than the fundamentals, then he has room for improvement without the political environment changing too much.
Of course, even if Trump was doing as well as Republican candidates for the House, he would still be trailing.