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 on Thursday.

Earlier in the day, Gingrich took a jab at Romney for saying he is focused on helping the middle class because poor people have a safety net.

"I really believe that we should care about the very poor, unlike Gov. Romney," Gingrich said.

Gingrich said both Romney and Democratic President Barack Obama think poverty can be solved with a safety net.

"What the poor need is a trampoline so they can spring up," he said. "So I want to replace a safety net with a trampoline."

Romney spokeswoman Amanda Henneberg responded that Gingrich was joining Democrats in "distorting Mitt Romney's comments."

Gingrich campaigned in Nevada as the state prepared for Saturday's caucuses. He toured a Las Vegas forklift manufacturing plant and held a roundtable with Hispanic leaders before ducking into a fundraiser.

Romney is favored in the state, which he won when he sought the GOP nomination in 2008.

Gingrich campaign officials see their second-place finish in Florida as translating into 16 delegates if they were awarded proportionally.

A statement from Lenny Curry, chairman of the Republican Party of Florida, said the 38 members of the party's executive board unanimously passed a rule last year authorizing the change.

"It is a shame when the loser of a contest agrees to the rules before and then cries foul after losing," Curry said.