So much has been written about the Joshua Generation, the young white evangelical Christians who pundits predicted would usher Obama into office in overwhelming numbers. Following such high-profile do-gooders as Rick Warren and Bono, moved to action by global poverty and environmental decay, these Christians were supposed to turn away from their parents' obsession with abortion and gay marriage and pull the lever for Obama. The truth, as always, is a lot more complicated. Young Christians liked Obama much better than Kerry: a third of white evangelicals ages 18 to 29 voted Democratic this time, compared with 16 percent in 2004. Still, a third is hardly a majority. And their grandparents liked Obama less: a quarter voted for him, compared with a third for Kerry. On the whole, Christians shifted negligibly to the left: 24 percent of them voted Democratic, compared to 21 percent in 2004. Exit-poll data...