In 2014, we put together an index to measure the electoral strength of the parties. Rather than focusing on the presidency, we broke partisan control into five categories: presidential, Senate, House, governorships, and state legislatures. We have updated our index using the mostly complete data for the 2016 elections and can conclude that the GOP is in the strongest position it has been since 1928. In many sub-categories, it is near an all-time high.
The following four paragraphs, taken verbatim from the previously linked article, describe our methodology:
“Our index is the sum of five parts: presidential performance, House performance, Senate performance, gubernatorial performance and state legislative performance. The first is measured by the party’s performance in the previous presidential popular vote. (In this, and all other measurements, third parties are excluded.)
“House performance is the average of the popular vote for the House and the average of the share of the House won by the party. This helps mitigate the effects of gerrymandering. Senate performance is the share of the Senate held by the party.
“Gubernatorial performance is the party’s share of governorships (again, with third party candidates excluded). We do not weight for population, for reasons explored further below. For state legislatures, we average four numbers: the share of state Houses and state Senates held by each party along with the share of state House seats and state Senate seats held by each party.
“This gives us five metrics, all of which run on a scale from 0 to 100. Adding them together gives us a scale from zero to 500. We then subtract 250 from the total. All this does is assign a score of zero to a situation where the parties are evenly matched, rather than 250. A positive score then means that the Republican Party is stronger while a negative score means the Democratic Party is stronger.”
Let’s walk the through the sub-scores, one by one. In the state legislatures, Republicans modestly improved their positioning from the already strong position they had achieved in 2014. Their sub-score is 63.2 (again, on a scale of zero to 100). If we exclude the Reconstruction period, the Republican Party has achieved a higher score in the state legislatures in three elections: 1894 (64.7), 1904 (64.6), and 1920 (66.5).
Likewise, in the governorships, the GOP emerged from 2016 stronger than it was after 2014. This is unsurprising, since Democrats were reduced to just 16 governorships. The GOP’s sub-score of 67.3 was surpassed only in 1920 (70.8) and during the late Civil War and early Reconstruction period (1864, 1866, and 1868).
The House, Senate and presidential charts pretty much speak for themselves:
If we put everything together in our final index, the GOP has a Trende-Byler score of 36.0, the highest score for the GOP since 1928 (when it scored a staggering 51.8). You can see the trend line here:
Note that the 2006 and 2008 elections now look decidedly like aberrations. It is hard to square this with an overall view of an ascendant Democratic Party, though there is still a lot of history to be written.
Here is the overall trend line, dating back to 1856.
The mean score over time is -3 points, and the median is -6. On a 500-point scale, this is basically nothing. This is consistent with the idea that elections over time tend toward parity. The standard deviation is 45, which is consistent with the idea that the GOP is in a strong position, but not an unusually dominant one.
With this, we can make some preliminary assessments of the Obama presidency. Obviously, this was not a successful period for party building. But how bad was it in a comparative sense? The index swung 70 points against Democrats from 2008 to 2016. Among two-term presidents, only Dwight Eisenhower (78.2), Franklin Roosevelt (98), Ulysses Grant (118.1) and Woodrow Wilson (137.2) presided over larger swings against their party. If we look only at FDR’s first two terms, he drops out, having lost only 40 index points. Given that President Obama oversaw reasonably robust growth throughout his term, unlike Eisenhower, Grant and Wilson, this is a jarring outcome.
Nixon/Ford’s loss would barely be larger (72.4) if we lumped them together. Of the 30 presidents in our sample, only nine fared worse than Obama (Lyndon Johnson, Grover Cleveland in 1892, Eisenhower, James Buchanan, William Taft, FDR, Grant, Wilson and Herbert Hoover). Of course, the largest swing for any president occurred under Hoover; in four short years the index swung nearly 137 points against the GOP.
This brings us to our final point: If you look over the broad sweep of history, this index has very little predictive power. The party that holds the presidency almost always loses strength, but the magnitude of that loss and how quickly it occurs is effectively random. Democrats should not be too discouraged by their present state of affairs. History teaches that it can be reversed, and rather quickly.