We’ve heard a lot in recent months about President Obama’s strength among the young. Indeed, he won 18- to 29-year-olds by a stunning 66 percent to 32 percent in November. But the latest Gallup poll shows that young people may be having second thoughts. In January, 75 percent of them approved of the job Obama was doing as president. That’s now 58 percent, a 17 percentage point drop. A quick look at the other end of the age spectrum, those 65 and older, shows a 12 point drop, from 61 percent in January to 49 percent today.