Super PACs backing Newt Gingrich have dominated media coverage of the GOP Florida primary that will be decided Tuesday, but their effect is starting to look less than super.

Two pro-Gingrich super PACs appear to have dropped out altogether. The biggest Gingrich-friendly super PAC spent $6 million in Florida backing the former Speaker, but a big chunk of it went into a ground operation that some argue was too ambitious for an independent group.

The role of super PACs in Florida may underscore the limits to how much can be accomplished on the presidential campaign trail by such unrestricted groups, some political observers say. The landmark Supreme Court decision Citizens United v. Federal Election Commission freed up these groups to raise big money quickly. But super PAC organizers must keep candidates at arm’s length, making it harder to round up volunteers and turn out voters in the field.

“What’s missing from the [Gingrich] campaign is anything relating to organization and infrastructure, and that will become important for Super Tuesday and later,” said Michael Malbin, executive director of the nonpartisan Campaign Finance Institute. “Super PACs will not help with that.”

The unrestricted super PAC known as Winning Our Future, run by a coterie of former Gingrich aides and bankrolled largely by casino magnate Sheldon Adelson, had touted its plans to launch a major voter ID and get-out-the-vote effort to counter candidate Mitt Romney’s substantial organizational advantage in the state. Adelson and his wife had given the super PAC $10 million.

But on the eve of the primary, Romney had re-emerged with a significant lead in the polls.

Of the $6 million that Winning Our Future spent in Florida, more than $4 million went to radio and TV ads, public records show. However, both the super PAC and the Gingrich campaign were swamped by more than $15 million in combined ad spending by the Romney camp, and by a pro-Romney super PAC known as Restore Our Future.

“We came into Florida with a 24-point gap” and turned the contest into one that is “too close to call,” Winning Our Future senior adviser Rick Tyler said. Tyler condemned what he said was millions in misleading ads aired by Romney and his allies and argued that Gingrich’s big crowds show that “Newt’s the candidate of the people.”

But Florida’s large, fragmented media market, combined with its diverse electorate, forces presidential contenders to spend both heavily and effectively, Tallahassee lobbyist and GOP strategist Mac Stipanovich said. In the case of Winning Our Future, Stipanovich said, “it was too little, too late.”

Stipanovich added, “You can’t do it in 10 days, and you can’t do it with $5 million. Not in Florida … you can’t just leap out of the bushes and go: ‘Boo. Here’s my $5 million,’ and win the Republican primary in Florida for president.”

Winning our Future is one of three pro-Gingrich super PACs that has struggled to live up to its billing. Denver-based conservative strategist Charlie Smith told Roll Call in November that he was launching a super PAC dubbed Solutions 2012 to rally tea party support behind Gingrich. But that PAC has made zero campaign expenditures since then, Federal Election Commission records show.

Another pro-Gingrich super PAC, Strong America Now, spent about $217,000 on direct mail in Iowa and South Carolina, FEC records show, but the PAC has reported no activity since then.

“Florida was a golden opportunity that seems to have been lost for Gingrich,” said Michael Franz, associate professor of government at Bowdoin College. Gingrich and his allies had too little time to build an effective ground game, Franz said.

“It’s probably hard for these groups to convince volunteers to work for them and not the candidate,” Franz said of super PACs. “So there is probably going to be more startup cost for a super PAC than for a candidate.”

In this unpredictable GOP primary, Gingrich could still deliver a surprise reversal of Romney’s double-digit lead in the polls. Super PACs are a new and largely untested campaign tool, Malbin noted, and they may yet prove capable of moving beyond broadcast ads to effectively turn out voters in the field. But he said the rules barring super PACs from coordinating with candidates by definition limit their scope.

“You really want to know which neighborhoods to work, you want to know where the candidate is going to be,” he said. “You can’t really make those decisions on the fly on the basis of newspaper reports and be as effective as you would be if you had inside knowledge.”

Winning Our Future Managing Director Gregg Phillips said running a super PAC is not that different from running any other kind of political campaign, but he acknowledged a key difference: “We’re spending a lot of our time acting like a campaign without a candidate, if you will.”