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President Obama will have to do more to convince young people to purchase health insurance than appear in a mock interview with comedian Zach Galifianakis, Charles Krauthammer said Tuesday.

“There's so many other problems, and Obama keeps having to postpone huge elements of it…he has to go on this ridiculous show last night, I think he's got a problem selling this,” the syndicated columnist and Fox News contributor said on “Special Report with Bret Baier.”

The latest enrollment numbers for ObamaCare released Tuesday would seem to agree. With just 20 days left to sign up for coverage under the Affordable Care Act, the Department of Health and Human Services said 4.2 million people had signed up through the end of February – far short of the unofficial goal of 7 million by the end of March.

Particularly troubling to the Obama administration is the lag in getting young adults to purchase coverage. Administration officials had hoped roughly 40 percent of enrollees would be in the 18 to 34-year-old range. But the latest report shows just a quarter of those who have purchased coverage are in that coveted demographic.

Which is partially why President Obama went on comedian Galifianakis’ show, “Between Two Ferns,” on FunnyorDie.com to talk about health insurance.

Krauthammer said the system was fundamentally flawed when it came to younger customers and the flaws would take more than marketing to overcome.

“You start with the fact that young people are averse to buying health insurance, because they have a sense of being invincible but it's worse with ObamaCare,” he said. “In the free market, 60-year-olds cost insurers about six times what a 20-year-old does, in terms of health care cost. So the premiums are six times as much.”

“But (Sen. Nancy) Pelosi and (Sen. Harry) Reid decreed in ObamaCare that it shouldn't be six times, it should be three times, which means that young people are paying twice the premium that they would in the free market.

“ So, not only is it a bad idea to start with, but they are clearly being overcharged as a way to subsidize others,” he said.

While the White House hailed the President’s appearance on the viral web series, noting that the interview was the number one driver in web traffic to HealthCare,gov, Krauthammer said that was simply not enough.

“You might want to sell it with a huge campaign, but it's a really bad deal, and that's why they're not getting a lot of buyers.”