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Voters this year look set to continue an odd pattern that's prevailed in presidential politics for a quarter century. They will elect either a candidate with a famous father or with no father.

The surviving serious contenders—Barack Obama, Newt Gingrich and Mitt Romney—all exemplify one of these two categories. For the seventh consecutive election, the winning candidate will be either a privileged prince with an adored, powerful patriarch, or an up-from-nothing scrapper with no relationship with his biological dad.