With its troubled launch and frantic final enrollment drive now history, the Medicare prescription-drug program is bracing for what could be its most significant public-relations hurdle yet.

In coming months, millions of older Americans and people with disabilities will face a lapse in coverage known as the “doughnut hole” once their annual drug spending hits $2,250. At that point, Medicare drug plans stop paying for medications and require members to absorb another $3,600 in out-of-pocket costs before coverage resumes. And even while the plans aren’t paying for their drugs, participants must continue to pay their monthly premiums.

Of the 11.8 million Medicare enrollees whose plans include a coverage gap, the Kaiser Family Foundation had estimated that 6.9 million of them could hit the doughnut hole, but a staff researcher said that number probably would be higher because of higher-than-expected enrollment.

Federal actuaries at Medicare, however, had said the number would be around 5.3 million, but they now say that figure is too high because of cheaper medications and strong enrollment in plans with no coverage gaps.

Time will tell who’s right. But because the overwhelming majority of Medicare plans include a doughnut hole, experts say it’s a safe bet that millions of seniors on fixed incomes will be struggling to pay for the life-sustaining medications they need but can’t afford without coverage.

The timing couldn’t be worse for the Bush administration and Congressional Republicans who’ve spent most of the year defending the new benefit. In the heart of the summer and fall election season, throngs of seniors stuck in the doughnut hole will have a new ax to grind.

“You’re likely to get a lot of folks hitting that doughnut hole after Labor Day and sometime right in front of the election, and that will certainly provide fodder for those who have criticized the benefit for not being generous enough,” said Michael Frank, the vice president for government relations at the Heritage Foundation, a conservative research center.

Covering the gap: Medicare administrator Mark McClellan defended the design, saying people who reached the gap already had saved more than $1,500 on their drugs through the benefit. He said plans must notify members how close they were to hitting the coverage gap in monthly statements.

Some enrollees can avoid the doughnut hole altogether by using cheaper generic drugs instead of brand-name medications. And once they reach the gap, McClellan said, they can still purchase drugs at the discounted Medicare price, which is lower than the retail price.

Medicare plans that offer coverage in the doughnut hole are available Nationwide, but are more expensive. As a result, only 10 percent of private plan enrollees and 27 percent of Medicare HMO members enrolled in such plans.

Read more on this topic.