Here’s something you may not realize about politics in the United States: We’re seeing fewer and fewer dynastic politicians.

That may seem unlikely during a period when George W. Bush was the most recent president, when Hillary Clinton, Jeb Bush and Andrew Cuomo are all regularly mentioned as presidential candidates, and where even the next generation of the Bush family is getting started in electoral politics. But nevertheless, it’s true, and the elections last week nudged the process forward a bit.

In particular, the 2012 results continued the recent trend away from dynastic senators. Of the 12 new senators elected, as far as I can tell, none of them have parents or other older family members who had been in elective office. The closest any of them get is Deb Fischer, whose father had a bureaucratic position in Nebraska state government as director of roads, and Heidi Heitkamp, whose younger brother became a state senator some time after her political career took off. I wouldn’t count either of them. That means there’s a decrease of two dynastic senators, with Jon Kyl and Olympia Snowe retiring....