by Patrick Appel

Doing a better job than I did, Kevin Drum explains the composition of the electorate: 

[A]bout 40% of the American population self-IDs as conservative, compared to only 20% who self-ID as liberal. You can argue all day long about what people really mean when they tell pollsters they're conservative, and you can argue all day long that liberals need to do something to change this instead of simply accepting it, but for any politician running for national office in the here and now, this is just the lay of the land. A hardcore conservative with hardcore conservative beliefs can count on a pretty big base of support right from the start, while a hardcore liberal candidate can count on bupkis. Conservative Republicans can win. Liberal Democrats generally can't unless they're running in very liberal congressional districts. If you're looking for a reason why liberal politicians tend to compromise more, you really don't have to look much further than this.

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