I think I've figured out why it is that so many Republicans wind up in the White House. Frustrated Democrats can blame the media.
Leading question: which way does the media lean, left or right?
Left, of course, and so naturally the media rallies behind the primary candidates of each party who lean to the left. They give fawning coverage for leftist Democrats (the leftist leftists), and ample coverage for the leftist Republicans (the leftist rightists - which is to say, the centrists).
Because America tends to vote for the centrist, the Republican nominee for president winds up in the White House more often than not.