In his presidential acceptance speech last week, Barack Obama gave a nod to his youngest and most loyal supporters, who, he said, had "rejected the myth of their generation's apathy." Indeed, voters ages 18 to 29 turned out more than they had since 1972, the first presidential election after the voting age was lowered from 21 to 18. They supported Mr. Obama by an unprecedented margin, casting their ballots 2 to 1 for him over John McCain, according to national exit polls. Final statistics on the youth vote were still incomplete late last week, but experts estimated that between 22 million and 24 million young people had voted in the election, an increase of at least two million over the previous presidential election, in 2004.