When Obamacare implementation began, its supporters said the program needed about seven million people to enroll by next March. Of that number, advocates said, a large portion -- about 40 percent -- had to be young and healthy, to cover the costs of insuring older, less healthy Americans.

As Obamacare's problems mounted, and it became more and more likely the system would not hit those marks, supporters began to lower their standards. First, they said Obamacare will be fine even if far fewer than seven million sign up. Then they said it will be fine even if far less than 40 percent are young and healthy.

Now, it's becoming apparent why Obamacare advocates are putting on such a confident face: They have no backup plan if their national health care scheme fails.

Last Wednesday Jason Furman, chairman of the Council of Economic Advisers, joined the Washington think tank Third Way for a wide-ranging discussion. Near the end of the session, Third Way scholar Bill Schneider brought up Obamacare. "Does the administration have any kind of backup plan — if not enough young healthy people sign up for the Affordable Care Act, what's going to happen?" Schneider asked. Noting that he teaches college classes, and his students don't seem particularly well-informed about Obamacare, Schneider continued, "What are you going to do if they don't sign up in large numbers? The numbers don't look that good for young healthy people."

Furman's response was not particularly encouraging for the administration. "We actually don't have a great demographic breakdown," he said, "but what we do know is that there was a big increase in enrollment in November relative to October, and we've seen increasing demand in December, although we don't have the final numbers and we don't have the demographic breakdown."

Furman continued: "We're obviously making — it's not a Plan B — Plan A is to do the most aggressive enrollment efforts you can, with young people, using social media. You see the insurance companies doing paid advertising. It's in the insurance companies' interest to sign these people up." Beyond relying on a social media campaign, Furman argued, the work done by private business on behalf of Obamacare could be critical. "We're doing everything we can, but I think unleashing the private sector and the large amounts they're going to spend on advertising might be even more important," he said.

Schneider was still curious. "But you have no particular backup plan?"

"There's a Plan A," Furman answered. "Which is to enroll as many young healthy people as you possibly can."