WASHINGTON (AP) — In a blow to the Obama administration on Medicare, government auditors Monday called for the cancellation of a costly bonus program for private health plans that congressional Republicans have criticized as a wasteful political ploy.

The nonpartisan Government Accountability Office said it's not clear that the $8.3 billion Medicare Advantage bonus program will improve quality because most of the money is going to plans just rated average. The auditors did find, however, that the bonuses would temporarily ease the pain of unpopular cuts to insurance plans under President Barack Obama's health care overhaul law.

Ahead of presidential and congressional elections in which seniors are a key group of swing voters, the administration has been working hard to portray itself as a good steward of Medicare, by cracking down on waste and fraud, improving benefits, and keeping costs under control. The GAO report could become a blemish on its record.