The president's fountain of youth is drying up

Then there are voters ages 18 to 29, among Mr. Obama’s most important supporters in 2008. The roughly 23.7 million “millennials” who voted in 2008 were 18% of the electorate, up 2.9 million voters over the previous presidential race. They gave Mr. Obama 66% to Sen. John McCain’s 32%, according to exit polls. This margin of roughly eight million votes was a major chunk of Mr. Obama’s overall edge of 9.6 million.

But youthful enthusiasm for Mr. Obama has waned. In October 2008, 78% of voters 18-29 told Gallup they would definitely vote that year. Now it’s 58%. …

Mr. Obama’s lead over Mr. Romney in the latest JZ Analytics poll among voters ages 18-29 is 49% to 41%. If young voters turn out this fall in the same numbers as in 2008 and give Mr. Obama this eight-point margin, it will take 2.8 million votes from Mr. Obama’s total and add more than 3.3 million to Mr. Romney’s tally.