WASHINGTON – The number of consumers purchasing health insurance under the Affordable Care Act has surpassed five million and President Obama is becoming increasingly optimistic that enough people have signed up to assure the law’s survival.

Appearing on WebMD last week, Obama told interviewer Lisa Zamosky that the program, popularly known as Obamacare, is “stable” despite early setbacks, assuring that healthcare firms that invested in the system likely will remain on board.

“Well, at this point, enough people are signing up that the Affordable Care Act is going to work,” Obama said before the official announcement that sign-ups had passed the five million mark. “The insurance companies will continue to offer plans.”

With the March 31 deadline to obtain insurance under the law quickly approaching, Obamacare has experienced a late surge. About one million people enrolled in the program over the last two weeks alone – more than signed up during the entire month of February.

“The last several days have been the busiest since December, with the Call Center taking more than 198,000 calls on Thursday alone –the busiest day since December 23—and more than 130,000 calls over the weekend,” said Marilyn Tavenner, administrator of the Centers for Medicare & Medicaid Services, the agency that oversees much of the ACA. “Last week, HealthCare.gov saw more than four million visits — and an additional one million visits this weekend.”

With two weeks to go before the sign-up deadline, “we’re continuing to work hard to ensure that every American who wants to enroll in affordable coverage… is able to do so,” Tavenner said.

Officials predicted the pace would quicken as the deadline approached, citing the experience in Massachusetts, which features its own law requiring residents to obtain health insurance. Part of the surge is attributed to Obama’s recent appearance on Between Two Ferns, an internet comedy series hosted by actor Zach Galifianakis aimed at a young audience – the same audience Obamacare is looking to attract. The show attracted approximately 19 million viewers.

“What we want is for people to know is that you can get affordable healthcare,” Obama said during the show. “Most young Americans, right now, they’re not covered and the truth is they can get coverage all for what it costs you to pay your cell phone bill.”

If enrollment maintains the current strong pace the Affordable Care Act could come close to registering six million consumers during the program’s first year – the revised number projected by the Congressional Budget Office. The administration initially targeted seven million, but a disastrous roll-out – featuring computer glitches and poor communications – led to the reduction.

Hitting the target won’t answer many of the concerns posed to officials that could confirm the vitality of the health of the program. The Obama administration has yet to reveal how many of the five million applicants have actually paid for their health insurance plans. And Obama himself, during the WedMD interview, said it has yet to be determined if the risk pool is sufficiently diverse to guard against the potential for skyrocketing premiums.

“You know, the impact in terms of the program has always been based more on the mix of people who sign up,” Obama said. “Do we have a mix of people who are gray-haired like me and may have some old basketball injuries and aches and pains, along with young people who are healthy and don’t really have any issues right now? Do we have a good mix of gender, in terms of men and women?”

And there is still a substantial amount of tinkering going on. Last week, for instance, the administration extended for a third time the Pre-Existing Condition Insurance Plan (PCIP), which was slated to expire on March 31. The program was created to aid individuals encountering financial problems purchasing insurance because of pre-existing medical conditions.

Aaron Albright, a spokesman for the Centers for Medicare and Medicaid Services, said the extension was adopted to provide those enrolled in PCIP “additional time to shop for new coverage while they receive ongoing care and treatment they need.”

The administration also has changed course on the impact sequestration – across-the-board budget cuts adopted by Congress – might have on the program. Originally the White House acknowledged that sequestration would affect a cost-sharing subsidy program that made direct payments to insurance companies on behalf of low-income individuals to offset spending on medical co-pays, deductibles and other out-of-pocket expenses.

Now the administration maintains the cost-sharing is no longer open to budget cuts – a decision that drew a sharp rebuke from Senate Republican Whip John Cornyn, of Texas.

“After all his claims that he was powerless to stop the effects of the sequester, the president is now conveniently exempting a portion of his failed healthcare law,” Cornyn said. “Rather than cherry-picking when the law applies in order to prop up Obamacare, President Obama should focus his attention on policies to grow the economy, increase jobs and address his flawed healthcare law.”

Congressional Republicans are continuing to fight the overall program. The GOP-controlled House on Friday, with a more substantial number of Democrats than normal joining in, voted 238-131 to delay the individual mandate – the Obamacare provision requiring everyone to obtain health insurance — until 2018.

The measure has no chance of making it through the Democrat-controlled Senate. The CBO concluded it would result in an estimated 13 million fewer people maintaining coverage than if the current mandate were kept in place. The Obama administration and health insurance firms both insist the mandate is necessary to prohibit consumers from waiting until they get sick to purchase coverage which would boost premium costs.