Fred Schulte, Holly K. Hacker | (TNS) KFF Health News Federal officials resolved more than a decade ago to crack down on whopping government overpayments to private Medicare Advantage health insurance plans, which were siphoning off billions of tax dollars every year. But Centers for Medicare & Medicaid Services officials have yet to demand any refunds — and over the years the private insurance plans have morphed into a politically potent juggernaut that has signed up more than 33 million seniors and is aggressively lobbying to stave off cuts. Critics have watched with alarm as the industry has managed to deflate or deflect financial penalties and steadily gain clout in Washington through political contributions; television advertising, including a 2023 Super Bowl feature; and other activities, including mobilizing seniors.