Over at the outstanding American Enterprise Institute blog, Karlyn Bowman reports that among the “millennial generation” (18- to 29-year-olds), President Obama’s job approval rating has, according to the latest Gallup poll, fallen from 75 percent in January to 58 percent today — a staggering 17-percentage-point drop. Among those 65 and older, Obama’s support has dropped by 12 points, from 61 percent in January to 49 percent today.

This is significant for several reasons. First, the huge numbers Obama amassed among young voters in November — he carried the millennial cohort by a margin of 66 percent to 32 percent — were among the most important signs of the GOP’s difficulties. If young voters lock in on a particular party early on, they often form a (voting) habit that is difficult to undo. If Obama had maintained anything like the initial support he had among young voters, it would have made the GOP’s challenge far more difficult. For the president to have lost so much support among young voters, so quickly, has to be unsettling to the White House and the Democratic party more broadly.

As for Obama’s double-digit loss of support among the elderly, that, too, is problematic, since the elderly are the most consistently reliable cohort when it comes to voting. Dropping below 50 percent among the elderly is a bad sign for Obama — and for Democrats running in 2009 and 2010, it is an alarming one. This negative trend among the elderly is largely attributable, I suspect, to Obama’s efforts to overhaul health care.

During the past six weeks, the president’s numbers have dropped in almost every category, and in some instances by a significant margin. For his legions of supporters, including much of the political class, it wasn’t supposed to be like this. Obama’s travails call to mind the counsel of the servant who supposedly greeted the returning, conquering Roman general, revered by the masses, with the words, “Respice post te! Hominem te memento!” (“Look behind you! Remember that you are but a man!”).

Barack Obama is but a man — and one with a fair amount of difficulties accruing.