What's the Reason for GOP Down-Ticket Dominance?

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If you’ve been keeping up with the wonky world of elections analysis, you’ve probably heard/read someone summarize the current balance of power in this (or a similar) way: Republicans have a gerrymandered “lock” on a House majority and a small-state advantage in the Senate, while Democrats, because of demographic change, have a big advantage in the 2016 presidential election. Proponents of this view typically recognize that President Obama’s low approval ratings in 2010 and 2014 contributed to the Republican waves in those years. But they lean on structural and demographics to support the idea that a Democrat in the White House and a GOP-controlled Congress is, for at least the near future, the new normal.  

The alternative (but not incompatible) narrative is that Republican control of Congress is mostly a result of President Obama’s low approval ratings. The president’s party typically takes a hit in midterm elections, as voters attempt to push back against presidents who overreach. So in that way, Obama’s losses can be viewed as a sort of normal midterm penalty that most presidents experience to varying degrees.  

These narratives aren’t mutually exclusive (and almost all analysts see at least some merit in both), but there’s a tension here: Which explanation explains more? In other words, in the big mix of factors that determines the outcome of elections, do structural and demographic factors matter more or less than the political climate and blowback against the president? And by how much?

I used data from the RCP partisan strength index (developed with RCP senior elections analyst Sean Trende last fall and updated a few weeks ago) to shed some light on this debate. Specifically our data indicate that 1) Obama faced a midterm penalty that was in some ways similar to past presidents and 2) state election results suggest that the structural features of congressional elections take a back seat to more enduring features of the political landscape – like the midterm penalty.

We’ve (Sort of) Seen This Movie Before

As Sean and I wrote a few weeks ago, the 2014 wave lifted Republicans to their highest level of strength in almost a century. But we have seen waves of this size in past midterm elections. Specifically, in 2010, 2006, 1994, 1982, 1974, 1970, 1966, 1958, 1954 and 1950, the opposition party expanded its power in waves of a similar or larger size.

This measure – similar to our partisan strength index – shows the two major parties’ strength outside the presidency on a scale from -200 to 200, where positive values indicate greater down-ticket Republican strength, zero indicates the parties have equal strength and more negative values indicate greater Democratic strength. The measure takes into account election results from the House, Senate, governorships and state legislatures (for more information, see the original index; the chart above is the same measure but, with the presidency omitted, we subtracted 200 rather than 250 so that zero indicates equal party strength). Colors show which party controlled the presidency.

Two patterns should stick out. First, during the blue swaths (Democratic presidencies) the index tends to increase. That means Republicans gained power when Democrats held the White House. Similarly, the index tended to decrease during the Republican presidencies as Democrats made gains down-ticket.

Second, the magnitude of the jump from 2012 to 2014 is big but not unprecedented. The index increased by 26.3 – a large amount, but far from the biggest midterm jump. In 2010, the index jumped by 47.5 points, and in 1994 it jumped by 55.7 points. In 2006 the index decreased (indicating improvement for Democrats) by 30.5 points and in 1982 it dropped by 23.6 points. In 1978, 1974, 1970, 1966, 1958, 1954 and 1950, the president’s party lost 25.3, 40.6, 24.0, 42.5, 46.0, 32.0 and 27.7 points, respectively. In other words, almost every president in the postwar era has lost a significant chunk of his party in at least one midterm election.

Yet in many of these past midterms, the opposition party didn’t enjoy the structural advantages the GOP now holds – or the demographic advantage that Democrats are presently enjoying. The Republicans did not draw the House map before taking Congress in 1994, and Democrats were once powerful in a number of small states (which provides an advantage in the Senate). The rapid growth of racial minorities is a relatively recent phenomenon – and both parties were able to win both in the general and midterm elections with a narrower racial turnout difference between elections.

This is not to say that gerrymandering, demographics, etc. did not help Republicans in the 2014 midterms. They almost certainly did. This is just to show that if we knew nothing about the demographic or structural factors affecting these elections and only looked at our index, Republican strength in 2010 and 2014 would not look that abnormal. It would simply appear as if Obama had two pretty bad midterm elections. And since there is debate about the importance of some of these demographic and structural parts of elections, it might be better to view Republican down-ticket dominance primarily as a result of normal political forces (like a standard midterm penalty or Obama’s relatively low approval ratings in 2010 and 2014) and secondarily as a result of GOP gerrymandering or Democratic demographic midterm woes.

States and Congress Move in the Same Direction 

But perhaps the more interesting feature of midterm blowback is that congressional and state elections – despite having different term lengths, occurring in different districts and running disjointed sets of candidates – are highly correlated.

For the statistically uninitiated: Correlation is a measure of the relationship between two quantities on a scale from negative one to one. A highly positive correlation indicates that when one quantity increases or decreases, the other tends to do the same. A highly negative correlation means that when one quantity goes up or down, the other tends to do the opposite. And a correlation of zero means that the two quantities have no relationship.

We measured the correlation between state power (based on gubernatorial and state legislative results on a range from -100 to 100, with zero indicating power parity, positive values showing greater Republican strength and negative values showing greater Democratic strength) and congressional power (based on House and Senate results on the same range and centered on zero in the same way that state power is) and found it to be 0.82 (a very high value).

Although the line showing state power over time tends to vary more widely than the congressional measure, they nonetheless tend to rise and fall together. They also typically cross zero – meaning that one party gained a rough majority of power – at the same time.  

This is interesting because the structural factors that apply to elections on one level don’t necessarily apply to elections on another level. Republicans may have drawn a favorable House map 2011 and had a helpful Senate map in 2014, but a different set of states had gubernatorial and state legislative elections. And even though each election had different candidates and each state faces somewhat different issues, these elections typically move in the same direction.

This again shifts emphasis away from the structural features of any particular type of election – be it gubernatorial, congressional or state legislative – or any demographic features of a particular time period. None of those structural or demographic details end up really derailing the overall typical penalty presidents face during midterms.  

Why This Matters

This might seem like an esoteric, inconsequential debate. At the end of the day, the reason one party controls one level of government and the other controls another is less consequential than what they do with that power.

But it does matter strategically. If Democrats are convinced that Republican strength down-ticket is structural, then they might withhold money and manpower from those races in 2016. And that could cost them. Similarly, if Republicans believe that their lock on the House is unbreakable, they might get complacent and endanger their majority.

So don’t lean too hard on structural and demographic features of elections – there are other important forces at work here.

David Byler is an elections analyst for RealClearPolitics. He can be reached at dbyler@realclearpolitics.com. Follow him on Twitter @davidbylerRCP.

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