WASHINGTON -- President Obama teased Ellen DeGeneres about the selfie she took at the Oscars and confessed to leaving his socks and shoes lying around while the first lady is out of town, but before the end of his Thursday appearance on the talk show he got to put in a plug for the Affordable Care Act.

That’s Obama's deal with popular media these days as the president enlists help in his effort to boost healthcare sign-up numbers before the March 31 enrollment deadline.

In recent days, Obama has filled out his March Madness brackets on ESPN, joked around with comedian Zach Galifianakis on “Between Two Ferns” and defended his “mom jeans” on-air with radio host Ryan Seacrest -- all with the agreement that he’d get a moment to pitch his healthcare plan.

The White House is aiming to bring young consumers into the fold, and not just because they represent roughly 40% of the uninsured population.

Young participants are more likely to pay into the system without drawing heavily on its benefits and are seen as key to ensuring the president's healthcare reform is economically viable.

Administration officials estimate they have signed up more than 5 million of the 6 million people they hope to enroll by the deadline -- a downward revision from the 7 million target they named before all the trouble with the rollout of the sign-up website, HealthCare.gov.

As healthcare experts predicted, young people are taking their time getting on board. Now, the White House is going after them through every media outlet and opinion leader they can mobilize. “Validators,” aides call them.

“In order to reach them,” said White House Press Secretary Jay Carney, ”we have to, you know, be creative.”

While the White House pushes that message, Republicans continue to argue that the reform law is fatally flawed and will harm the other end of the age spectrum. As Obama traveled to Orlando on Thursday, the office of House Speaker John A. Boehner (R-Ohio) said that, while in Florida, the president should answer questions about the reform law from seniors.

"The president has focused plenty of time and energy of late on young people," Boehner's office said in an afternoon news release. "Isn’t it time he directly address older Americans who are bearing the brunt of his healthcare law? He shouldn’t leave Florida today without doing so."

In his remarks on the road, Obama planned to focus on his economic agenda -- and, always, where healthcare reform fits into it. As he participates in a roundtable and delivers remarks, however, his staff and pitch people keep a tight focus on the healthcare push.

Sports media and stars have played a major role in the final push. This week, NBA All-Star Kobe Bryant did an interview on Dan Patrick’s radio sports show in which he encouraged people to get coverage before the 2014 sign-up period ends. Former NBA All-Star Grant Hill called in to sports radio shows Wednesday in Miami, Dallas and Houston.

Miami Heat player Shane Battier promoted the healthcare plan in a conference call the other day with reporters. As he spoke, the administration released a report showing that nearly 2 million people went to emergency rooms each year because of sports-related injuries.

On Thursday, the White House ran a social media campaign trying to drive traffic to GamePlan4Me.com, a website promoting the sports benefits of having health insurance and featuring athletes such as Bryant, Yankees pitcher CC Sabathia and Giants wide receiver Victor Cruz. NBA forward Kevin Durant sent a #GetCoveredNow tweet to his 6 million Twitter followers.

Of course, some of the pitch men and women are not as famous.

Health and Human Services Secretary Kathleen Sebelius on Thursday traveled to New Orleans and Fort Worth to highlight local efforts to help people enroll.

White House Chief of Staff Denis McDonough recently called in to a sports talk radio show in Cleveland to talk up GamePlan4Me.com.

Carney said the White House is “comfortable” with the pace of enrollment but thinks it can round up more young people before the deadline.

When Massachusetts ran its first enrollment, he said, “the demographic breakdown at the various stages of enrollment in the open-enrollment period is mirrored by what we’ve seen in our figures.”

“I don't think anyone would argue that Massachusetts did not get, in the end, either sufficient numbers or the sufficient demographic breakdown that it needed to function effectively,” Carney said. “So we feel confident that we'll do the same.”

christi.parsons@latimes.com

Twitter: @cparsons