Something very unusual by historic standards happened in this year’s election: there were lots more Republicans than Democrats in the electorate.
After the exit polls were reweighted to reflect the final popular vote result, Republicans outnumbered Democrats by 5 points in the AP VoteCast survey and by 4 points in the network exit polls.
Historically, this is practically unheard of. Democrats have held a longstanding advantage in party identification that dates back to the New Deal, with Republicans drawing even on only a couple of occasions — the 1994 Republican Revolution and the immediate post-9/11 period.
Until Ronald Reagan remade the Republican Party’s image in the 1980s, Democrats held a massive advantage in party ID that often reached 2-to-1 in the 1960s and ‘70s.
Only after Reagan’s 1984 landslide did the modern narrow Democratic advantage take hold, where it’s stayed for the most part ever since.
The historic Democratic identification advantage has been with us since the advent of modern polling and has been an inexorable fact of political life for the better part of a century.