ORLANDO, Fla. • Florida may be Newt Gingrich's Waterloo.

After storming into the state with a head of steam from a surprising win last Saturday in South Carolina, Gingrich's support has waned, and polls now suggest that he could lose Florida's primary when voting ends Tuesday, perhaps by a wide margin.

He has run into a newly energized, hard-hitting opponent in Mitt Romney, a TV-dominated megastate where he can't afford to play and a diverse state in which transplanted Northeasterners and Midwesterners aren't as welcoming to his message.

At the same time, the party establishment is rallying to stop him. And he heads from Florida into a weeks-long stretch with no TV debates, once the lifeblood of his cash-poor campaign.

A solid loss would kill the boomlet he enjoyed in South Carolina and severely limit his ability to challenge Romney. He could come back again — he has twice already in this long campaign — but the cash and the calendar work against him more with each passing week. Instead, they work for Romney.

"Gingrich's momentum from his South Carolina victory appears to have stalled and ... Romney seems to be pulling away in Florida," said Peter A. Brown, assistant director of the Quinnipiac University Polling Institute.

Polls punctuated the turnaround.

A Quinnipiac poll Friday found Romney with the support of 38 percent of likely Florida primary voters, Gingrich with 29 percent, Rep. Ron Paul of Texas with 14 percent and former Sen. Rick Santorum of Pennsylvania with 12 percent.

With 3 in 10 likely voters saying they still might change their minds, it's possible that Gingrich could gain again. However, Brown added, "with the debates now over, Gingrich will need some other way to reverse the tide that appears to be going against him."

Other polls show a similar lead for Romney: The Rasmussen poll reported a 17-point shift, from a Gingrich lead of 9 points Monday to a Romney lead of 8 points Thursday.

Several factors combined in Florida against Gingrich, a former speaker of the House of Representatives.

First, Romney fought back hard.

The former governor of Massachusetts came out swinging against Gingrich in a Florida debate Monday, then did it again Thursday. He slammed Gingrich for airing an ad that calls Romney anti-immigrant, ripped anew Gingrich's paid work for the troubled housing agency Freddie Mac and ridiculed his proposal to colonize the moon.

Second, Romney could afford to advertise heavily, the only candidate who had the means to do that in a state with 10 media markets.