Sure, you can draw up a list of issues where he has been out of step with most Republicans. But the party’s last two nominees had longer lists, with more important issues on them. Mitt Romney had a recent history of supporting legal abortion, and his record on the top domestic issue of the past few years – – health care — put him at odds with conservatives. Senator John McCain had broken with them on taxes, guns, climate change, stem cells, immigration, campaign finance and more.

Most of the last seven Republican nominations have gone to people to the left of the party’s center of gravity, and none of them to anyone on its right. Why is that? Think of the nominating contest as a competition for the affection of three groups: the activist-conservative base of the party (groups like the Club for Growth and the Family Research Council), the party regulars (people who consider themselves “conservative” but not “very conservative”), and the party establishment (elected officials, campaign operatives, big donors).

The base typically splits its vote among several candidates, including a few who don’t strike the regulars as commander-in-chief material. The establishment always picks someone who passes that test, and usually picks him early in the process, before the first primary votes are cast. (Unlike the base, it doesn’t display much imagination in making its choice.) So the establishment candidate usually wins.