WASHINGTON (AP) Fitch Ratings has downgraded the United States governments credit rating, citing rising debt at the federal, state, and local levels and a steady deterioration in standards of governance over the past two decades.

The rating was cut Tuesday one notch to AA+ from AAA, the highest possible rating. The new rating is still well into investment grade.

The decision illustrates one way that growing political polarization and repeated Washington standoffs over spending and taxes could end up costing U.S. taxpayers. In 2011, the ratings agency Standard & Poors stripped the U.S. of its prize AAA rating and also pointed to partisan divisions that made it difficult for the worlds biggest economy to control spending or raise taxes enough to reduce its debt.

Reduced credit ratings over time could raise borrowing costs for the U.S. government. The Government Accountability Office, in a 2012 report, estimated that the 2011 budget standoff raised Treasurys borrowing costs by $1.3 billion that year.

At the same time, the size of the U.S. economy and historic stability of the U.S. government has kept its borrowing costs low, even after the Standard & Poors downgrade.