WASHINGTON — Even as the White House highlighted the 2.2 million total enrollments in the Affordable Care Act on Monday, officials said not to focus too much on that top line number when determining the long-term sustainability of the health care overhaul.

Average monthly enrollment in Minnesota’s marketplace, MNsure, is on a pace that would miss even the lowest state projections for sustainability, which could mean budget shortfalls by 2015, when the exchange has to stand on its own.

But White House officials said Monday that overall enrollment is not as important for sustainability as the age breakdown of those signing up for insurance. Younger is better, and, at least on the federal level, they’re confident they’ll hit a sustainable level before open enrollment ends in March.

Asked about state exchange enrollment issues, White House spokesman David Simas said, “When we’re looking at the question of sustainability of the marketplace, the mix is the most important.”

“If you look at what’s important for sustainability, it’s the mix, not the aggregate number, but the composition of what that marketplace is going to be,” he said at a roundtable with reporters on Monday.

On the federal level, the Obama administration says it wants at least 25 percent of ACA enrollees to be under the age of 35; according to a report released on Monday, that group makes up 24 percent of the total enrollments so far. In Minnesota, MNsure officials want to keep the median age of enrollees at 40 or under. When state officials released updated enrollment data earlier this month, the median age was 48.

Simas said the Obama administration plans to launch a big PR campaign to attract newer and younger enrollees, but only in states relying on the federal exchange. States like Minnesota will continue outreach efforts on their own, he said.

“States are doing a very, very good job in terms of specifically tailoring their outreach to their constituents,” Simas said. “The Paul Bunyan campaign in Minnesota is interesting and I think they’re doing a great job.”

Enrollment numbers a political football

The ACA enrollment reports have turned into as much of a political football as the monthly employment numbers. On Monday, the White House said the report shows the program’s positive trajectory, that, yes, younger enrollment needs to grow but that it’s likely to do so before the March 31 deadline.

“We feel that we’re in a very solid and good place, relative to the mix,” Simas said.

But the 25 percent analysis relies on a December Kaiser Family Foundation report, which differs from the Congressional Budget Office’s initial projection that at least 38 percent of enrollees should be under 35. Thats’ what Republicans seized on after the numbers came out — House Speaker John Boehner’s office put out a statement saying, “youth enrollment has been a bust so far.”

White House chief of staff Denis McDonough told reporters Monday that CBO’s figures don’t represent a “magic number.” But both he and Simas said they expect the enrollment in the younger, “deadline-driven” demographic to grow before the end of March. They said national ACA enrollment trends line up nicely with the 2007 rollout of the Massachusetts health care exchange, where under-35 enrollment increased as the deadline approached.

“We’ll be focused as much on the mix of the enrollments as on the overall number,” McDonough said.

Devin Henry can be reached at dhenry@minnpost.com. Follow him on Twitter: @dhenry