You may have noticed a few comments on the site recently suggesting that, during the 2016 Democratic Primaries, a candidate’s strength in states that will almost certainly vote for the Republican candidate in the general election is less significant than primary strength in other states.
But is this reasoning sound? How closely does a candidate’s state-by-state primary strength correlate with strength in the general election?
It’s a problematic question to investigate for the simple reason that most primaries are not competitive in the long term—most successful candidates essentially “win” quite early on, and thus win most subsequent states, denying us the opportunity to gauge their state-by state primary strength. What we need is a long, close primary race to examine. Fortunately, we have one, the 2008 contest between Barack Obama and Hillary Clinton, and the subsequent general election between Obama and John McCain.
Here is a map showing the 2008 primary states “won” as far as voting goes, with Obama in purple, Clinton yellow. The states Obama went on to win in the general election against McCain are outlined in blue.
In the primary, Obama was strongest in the “red” states. Clinton won most the of heavyweight “blue” states (CA, NY, PA, OH, NJ). And yet Obama won these states comfortably in the general, and had a very strong overall victory, despite losing the majority of his “red” primary states to McCain.
A Democratic primary candidate being strongest in “red” states does not seem to have any effect on general election performance.