MGM Resorts has found an ace that could possibly turn the tide in their favor and stop the tribes from building a casino in Connecticut.

The trump card that MGM Resorts is dangling to stop Mashantucket Pequot and Mohegan tribes is no other than the new letter from U.S Republican Sen. John McCain, according to The CT Mirror report.

On Tuesday, McCain prodded Interior Secretary Ryan Zinke to disavow an advisory letter that the Obama administration issued to the two tribes. The advisory letter, according to the report, indicated that their proposal would not jeopardize existing compacts with Connecticut.

For MGM, McCain’s letter is a timely development since disavowing Obama’s advisory letter will weaken Mashantucket Pequot and Mohegan’s argument that a new casino off tribal lands would jeopardize more than $260 million in annual revenue sharing the tribes now pay to Connecticut.