A re-posting from WFAE's The Party Line with the graphics included:
As many of the post-election commentaries pronounce a host of reasons (the better candidate in political workmanship, the novice challenger, a localized race that went national) why the once disgraced, now redemptive, Sanford won, we might want to view a more important component of his victory: the voters of the first congressional district.
If it wasn’t for Sanford and his baggage, most all analysts would have written off the Lowcountry contest as a “safe Republican” seat, due to the fact that Mitt Romney carried the district by 18 percent in the 2012 presidential election.
In fact, this kind of “landslide” district has become the national norm in U.S. House contests.
In Nate Silver’s analysis of the 2012 U.S. House races, he found that in 2012, only 35 districts—less than ten percent of the 435 contests—were “swing” districts, meaning that the district results were within five percentage points of the national popular vote margin.
More importantly, it appears that House elections are showing a closer alignment with the overall electoral patterns of voters, especially using the presidential returns.
In the 1st Congressional District election, I took the precinct returns from the 2012 presidential election and asked, would those presidential results have any possible predictive power to an election six months later?
Meaning, would Romney performance in each precinct give an indicator of Sanford’s performance as well? Conversely, would Obama’s performance indicate how Colbert Busch would perform as well?
Using Romney’s performance on the horizontal axis and the preliminary numbers for Sanford on the vertical axis for the largest county (Charleston) in the 1st District, here’s the result:
Romney’s Vote Share in 2012 Presidential Election and Sanford’s Vote Share in 2013 Special Election in Charleston County
With a few exceptions (most notably a precinct where Romney got only 8% of the vote, but Sanford got 34% of the vote), the vote share alignment between Romney and Sanford is pretty striking.
And even though Obama won Charleston County in 2012, the relationship between his vote share and Colbert Busch’s vote share in that county is also striking.
Obama’s Vote Share in 2012 Presidential Election and Colbert Busch’s Vote Share in 2013 Special Election in Charleston County
So what might this mean? One explanation might be that the United States is becoming more “parliamentary” in its national legislative elections: it doesn’t matter who the candidate is (hiking boots and all the relevant baggage), but what does matter is the voters’ party allegiance.
This would tend to make us more along the lines of British elections, where the voters cast their ballots for the party; the “candidate” standing as that party’s choice to be the member of Parliament really doesn’t matter, because that candidate was picked by the party without any voter input.
Granted, U.S. primary elections have become “the” election, rather than the general election, because, as Silver pointed out, more and more districts are “landslide” in their behavior (117 Democratic and 125 GOP districts in 2012’s House elections were 20 points or more above the national popular vote).
So, it appears that even in a contest, headed by candidate who suffered from both self-inflicted wounds and a deep drive to win, the district behaved as it should—and gave the landslide win that most of us should have expected, but didn’t.