LAS VEGAS (AP) — Republican presidential candidate Newt Gingrich, defeated in Florida by a wide margin, is challenging rules in the state that handed all 50 delegates to Mitt Romney.

The Gingrich campaign planned to send a letter to the Republican Party of Florida asking that it “enforce existing rules” that say delegates should be awarded proportionally, a campaign spokesman said Thursday.

It was the second time the Gingrich campaign complained about primary rules after suffering a setback. When the campaign failed to meet the requirements of getting on the primary ballot in Virginia, it went to court with other candidates to have the requirements annulled. A federal judge declined to do so.

The move came as Gingrich lost the endorsement of real estate tycoon Donald Trump, which his campaign had thought was in the bag. Trump threw his support behind Romney Thursday.