It was a key voting block for President Barack Obama in his historic election victory in 2008 and re-election in 2012: the youth vote. In fact, according to exit polls, roughly 60 percent of 18- to 29-year-old voters backed his re-election bid.
But a poll out this week by Harvard University's Institute of Politics suggests that the president's support is bleeding from his broad base of America's youngest voters, just when he is pushing for their help to prop up his troubled Affordable Care Act rollout.
"A critical factor in the election and re-election of Barack Obama, America's 18- to 29-year-olds now rate the president's job performance closer to that of Congress—and at the lowest level since he took office in 2009," Harvard Institute of Politics Director Trey Grayson said in a press release.
According to the Harvard poll, only 41 percent of millennials approve of the president's job performance. That marked an 11 point drop since April but is in line with his broader approval rating nationally (Real Clear Politics polling average: 44 percent approve versus 55 percent disapprove).
Perhaps more shocking? Of the 55 percent of young voters who say they voted for Obama in 2012, only 46 percent said they would do the same again. And 52 percent of the youngest voters, 18 to 24, said they would support recalling or replacing Obama if they could, according to the Harvard Poll.
When America's 18- to 29-year-olds were asked if they approved or disapproved of the comprehensive health reform package that the president signed into law in 2010, known as Obamacare, a solid majority disapproved (56 percent). By a margin of more than 2-to-1, millennials believe that the quality of care will get worse under Obamacare (18 percent: care will improve; 40 percent: care will worsen) and 51 percent believe their cost of care will increase.
More troubling, as young, healthy enrollees are critical to Obamacare's ultimate success, only 29 percent of the 22 percent of millennials without health coverage said they will enroll in the program.
The latest poll numbers come as Obama held a youth summit at the White House on Wednesday, where he urged participants to help other young people enroll in a plan through the health law's exchanges. He says coverage will cost most young people less than $100 a month.
On CNBC Thursday night, "The Kudlow Report" gathered a small youth summit of its own to gauge college student reaction to the sobering poll. The participants included two members of the Columbia University Democrats, freshman Jordana Narin and sophomore Ankeet Ball; and two Republicans, Sophie Miller, a senior at Boston University, and Harper College's Charlie Kirk, founder and executive director of Turning Point USA.
Kirk attributed the president's sinking ratings to a "perfect storm" of problems: NSA surveillance, a rocky job market and Obamacare.
"For the first time in the last 50 years we're seeing young people feel the negative effects of their vote almost immediately," Kirk said. "They're paying higher premiums, crippling student loan debt, and they can't find a job. They're tired of hearing the rhetoric of the president when they're seeing the harsh reality of the policies."
Miller agreed that the effects of Obamacare are not unnoticed by her generation.
"Obamacare is really hurting young people, young millennials like myself," she said. "For example at Bowie State University in Maryland, their health care costs went from $54 a semester, just about $100 a year, to $1,800. That is not sustainable, and it's just not acceptable."
But the response was not unanimously opposed to the president's signature health-care law.
"I think when people talk about Obamacare they forget about all the positives," Narin said. "The fact that for me right now, I'm not paying any higher premium. I'm allowed to stay on my parents' health insurance until I'm 26 because of Obamacare. When I find my own plan, which I plan on doing once I turn 26, I will not be denied based on preexisting conditions."
Ball said criticism of Obamacare is rooted in deeper economic problems.
"The job market has not been looking great for recent hires and recent graduates, but if the job market increases and serves graduates better, that way young people as it stands will be able to finance Obamacare," he said.
—By CNBC Producers Ben Thompson and Elizabeth Schulze