Tuesday, September 16, 2014

Another Look at Electoral Change

Last fall, I posted some data on the changes in Democratic and Republican support in the states in presidential elections, in part in response to observations made by a number of pundits and politicians that there is an increasing Democratic "lock" on the Electoral College.  As I stated then, this sort of chatter even included speculation that Texas could "turn blue" in the not-so-distant future.  Indeed, this idea was recently repeated by Rand Paul, who cautioned Texas Republicans that they need to soften their approach on issues such immigration, or Texas "will be a Democratic state within 10 years."

I return to the issue of electoral change in this post to provide a somewhat clearer visualization of the trends, as well as a more precise account of their electoral impact. 

The strategy used in the previous post focused on plotting the trends in party support from 1972-2012, separately, for each state (see Democratic gains here and Republican gains here).1  I use the same data here but approach the analysis somewhat differently, focusing on the overall change in the centered Democratic share of the two-party voter from the 1972-1980 elections to the 2004-2012 election.   Specifically, I look at the average expected Democratic vote share (based on the trend over time) for each state in each time period and then compare the two periods to ascertain where the parties gained and lost the most support. Centering the vote around the mean state outcome permits a comparison across states without having to also consider factors (national tides) that affect the level of party support from one year to the next.

The figure below captures both the direction and magnitude of changes in party fortunes in the state-level presidential election outcomes.  In this figure, the ubiquitous chromatic devices of red and blue are used to identify states where the trend over time has favored Republicans (red) or Democrats (blue).  The blunt end of the arrow represents the state average during the 1972-1980 elections, and the point at the head of the arrow designates where the states end up, on average, for presidential elections from 2004 to 2012.  It is important to recall that party support is expressed relative to other states, in each year. For instance, in a Republican blowout year, such as 1972, a state like Minnesota, where George McGovern ran about 10 points better than he did across all states, could still be lost by the Democrats.  Despite McGovern's loss there, Minnesota in 1972 is still a strong Democratic state, relative to all other states.  

Changes in Party Fortunes in State-level Presidential Election Outcomes
Changes in Party Fortunes in State-level Presidential Election Outcomes
So what does this figure reveal in terms of a growing Democratic advantage in the Electoral College?  In very gross terms, there is a an important trend in favor of Democratic presidential candidates. Looking just at the direction of movement (ignoring magnitude), there are 29 states that have seen Democratic gains, and 21 states where Republicans have gained strength.  In terms of electoral votes, the states where Democrats have made inroads control 366 electoral votes, while the states with Republican gains control just 169 electoral votes.  This is a substantively large and meaningful difference.  However, it may overstate the case somewhat, since some states in which the parties gained strength were already in the Democratic or Republican column and only became more strongly partisan; and in a few states where a party gained strength (e.g., Mississippi and Georgia for the Democrats, and Minnesota and Wisconsin for the Republicans), their position is improved but they are still at a distinct disadvantage.  And there are a handful of states where movement was very slight, though on balance in one party's favor.  

It's also worth noting that there is no support for the Texas-turning-blue argument, as Texas has gone from leaning Republican to solidly Republican over the past forty years.

Another way of assessing the importance of partisan change is to focus on cases of conversion (switching from one party to another) or changes in swing status (moving from competitive to non-competitive or from non-competitive to competitive.  The figure posted below highlights states that fall into either of these categories.  The vertical dashed lines are are -2 and +2 percentage points, representing a fairly tight band of competitive outcomes.  There is only one state (West Virginia) that can be described as clearly switching from from one party (Democratic) to the other (Republican), while the remaining twenty states moved into or out of the competitive zone.  Across all twenty-one states whose competitive status changed, six states representing 40 electoral votes moved in the Republican direction, while fifteen states representing 188 electoral votes moved in the Democratic direction.

Changes in Party Support, Highlighting "Swing States" 

From this perspective, there has been clear and important movement in the direction of the Democratic party.  The number of states that have moved through this zone in the Democratic direction (and the number of electoral votes associated with them) improves the Democratic position substantially over the past forty years.  A couple of caveats. First, this is only one way to cut the data and the designation of the competitive zone is admittedly arbitrary (as most such designations would be).  Second, this discussion places a premium on a certain type of change and ignores cases in which parties increased their grip on already friendly states.  To be sure, there are a number of Republican and Democratic states where this has happened, and the Republican party has a slight edge in this category.  

The table below uses data on party support and electoral votes to illustrate more precisely the magnitude of the increased Democratic advantage.  The cell entries in the right two columns are the predicted number of Electoral Votes going to the Democratic candidate based on three different national vote models (mean Democratic votes of 48%, 50%, and 52% across the states), along with the expected levels of support (taken from beginning and end points of the arrows in the figures above) in the states and their associated Electoral votes in the 1970s and the 2010s.

In the current period, Democratic candidates have a distinct advantage in close national contests. If the average state-level vote is 50%, the expected Democratic Electoral Vote count is 319.  If the average Democratic state vote drops to 48%,  Republicans would be expected to pick up Colorado, Florida, Nevada, and Ohio, but Democrats would still have a fighting chance, with an expected Electoral Vote count of 257.  And, of course, if Democrats carry 52% on average across the states, they win a comfortable Electoral Vote margin.  What is most impressive here is not just the Democratic advantage, but how that advantage has shifted since the 1970s, where the Democratic Electoral Vote was much more proportional to the national popular vote.  

It is important to remember that the change in the Democratic advantage is not affected just by changes in patterns of party support across the states but also by changes in the Electoral Votes awarded to the states.  In fact, changes in the distributions of electoral votes have muted the shift in Democratic advantage slightly. For instance, at a 50% average state vote the expected Electoral Vote of Democrats in the 2010s would be 333 if there had been no change in the Electoral College since the 1970s.

There is still no evidence of a Democratic "lock" on the Electoral College, but the data presented here do make a clearer case that Republican presidential candidates face an uphill battle, and that their position has deteriorated over time.  The political landscape has changed appreciably in the last forty years and that change is politically consequential. Of course, all of this raises interesting questions about the causes of the changes in party support, questions I will take up in my next post (soon, I hope).

1See the original post for a more detailed explanation of have the expected state vote is calculated. Note that these figures reflect a correction for the trend in North Carolina.