Which party is the majority party? Neither

Which party is the majority party? Democrats like to note that their nominees have won pluralities of the popular vote in six out of the last seven elections. Republicans like to point out that their party has won majorities of the House in 10 of the last 12 House elections (and popular-vote pluralities in nine of the last 12).

Both claims are accurate, as far as they go. But the fact is that in this era of partisan polarization and partisan parity, both parties have had difficulty in winning actual majorities (as in 50 percent plus one) of the popular vote.