Michael Barone‘s latest column examines how President Obama’s policies have affected one of his largest sources of support: young adults.

What do young Americans want? Something different from what they’ve been getting from the president they voted for by such large margins.

Evidence comes in from various polls. Voters under 30, the Millennial generation, produced numbers for Barack Obama 13 percentage points above the national average in 2008 and nine points above in 2012.

But in recent polls, Obama’s approval among those under 30 has been higher than the national average by only one percentage point (Quinnipiac), two points (ABC/Washington Post) and three points (YouGov/Economist). …

… The reasons for Millennials’ decreased approval of Obama become clear from a Harvard Institute of Politics (IOP) poll of 18- to 29-year-olds conducted in November.

That poll shows Obama’s job approval dipping to 41 percent, down from 52 percent in April 2013 and the lowest rating in any IOP survey.

One reason for the decline is Obamacare. Only 38 percent approved of Obamacare (39 percent approved of “the Affordable Care Act”). Only 29 percent of those who were uninsured said they would definitely or probably enroll in the health-insurance exchanges.

Those results were registered five to nine weeks after the October 1 Healthcare.gov rollout. Tech-savvy Millennials must have been astonished that the government produced a website that didn’t work.

They also perceived, accurately, that Obamacare health insurance would cost them a lot. The law passed by Democrats elected in large part with Millennial votes was designed to have people under 30 subsidize the insurance premiums of those older, less healthy people over 50.