Newt Gingrich isn’t the only one trying to beat Mitt Romney in Florida.

Several liberal groups are funding new ad campaigns in the Sunshine State targeting the vulnerable GOP presidential candidate, part of an unusually bold effort by Democratic supporters to bolster President Obama’s chances in November by influencing the Republican primaries.

The plans include a $1 million ad buy from the American Federation of State, County and Municipal Employees, the nation’s largest public employee union, which is focusing on Romney’s history as head of the private-equity firm Bain Capital. The Service Employees International Union and Priorities USA Action, a pro-Obama super PAC, have also jointly launched a Spanish-language radio campaign in Florida accusing Romney of having “two faces” on immigration issues.

The push signals a growing belief among Democrats that they may have a real chance at helping to derail Romney, who has long been viewed as Obama’s most formidable GOP opponent but is reeling from a loss to Gingrich in South Carolina. Gingrich and Romney are locked in a tight race ahead of Tuesday’s Florida primary.

While unions and other groups commonly run political ads supporting their candidates in the general election, this is something different — an unusually direct intervention by one side into the other party’s primary race, political strategists said.

“The target of opportunity presented itself, and we decided to take advantage of it,” said Seth Johnson, assistant director in ­AFSCME’s political action department. “Before South Carolina and after South Carolina, Mitt Romney is still the front-runner. We thought it was a good time to educate Florida voters about his record.”

Johnson added that it was “a pretty rare occurrence” for the union to get involved in a Republican primary.

Romney spokeswoman Andrea Saul said the efforts were part of an “all hands on deck” strategy by Democrats to “kill Romney” in the same way Obama targeted Hillary Rodham Clinton in 2008.

“The last thing the White House wants is Mitt Romney as an opponent,” Saul said, adding that Obama “is desperate to distract from his failed economic record.”

For months, Democrats and affiliated groups have focused their attacks almost exclusively on Romney as the presumed GOP rival to Obama, largely ignoring Gingrich, Rick Santorum and other Republican hopefuls. The efforts have included news conferences, Web videos and other tactics aimed at getting news coverage.

But until now, pro-Democratic groups have bought relatively few broadcast ads during the GOP primary season, which has been dominated by spending from conservative groups backing Romney or opposing Obama, according to expenditure data. One pro-Romney super PAC, Restore Our Future, has spent $5 million in Florida, according to the Federal Election Commission.

“There’s no doubt he’s put his campaign in the weakest position it’s been in months,” Bill Burton, a Priorities USA spokesman and former White House aide, said in regard to Romney.

The AFSCME ad compares Romney to Rick Scott (R), the unpopular Florida governor who headed a hospital conglomerate prosecuted for Medicare fraud in the 1990s. The message dovetails with criticism this week from Winning Our Future, a pro-
Gingrich super PAC that plans to run as much as $10 million worth of ads against Romney in Florida.

The AFSCME spot, running in Tampa, Orlando and West Palm Beach, focuses on Damon Corp., a medical testing firm that was prosecuted for Medicare fraud committed while it was owned by Bain Capital, which was then headed by Romney.

The ad shows Romney morphing into Scott with the words: “Corporate greed. Medicare fraud. Sound familiar?”

The radio ad from Priorities USA and SEIU focuses on Romney’s Spanish-language advertising and other outreach efforts with Hispanic voters in Florida, which the groups call “insincere and disingenuous.”

Romney has taken a hard line on border policies during the primaries and has vowed to veto the Dream Act, a bill that would create a path to citizenship for young illegal immigrants who are college students and military service members. He and Gingrich are both vying for support among the state’s large Hispanic bloc, including its influential Cuban American population.

“Mitt Romney has no shame,” the SEIU radio ad’s narrator says in Spanish. “He shows one face to the Hispanic community and another, completely different one to everyone else.”

Eliseo Medina, SEIU’s secretary-treasurer, said Romney “happens to be the one who went beyond the pale with his recent comments. Newt Gingrich and Rick Santorum shouldn’t feel neglected. As the campaign goes on, we will be evaluating them, too.”

Broadcast ads aren’t the only tactic available to Democratic-aligned groups hoping to influence the Republican contest. American Bridge for the 21st Century, a liberal super PAC that focuses mostly on opposition research, blanketed Columbia, S.C., with hundreds of hot-pink leaflets trumpeting Romney’s support for gay rights during the Massachusetts phase of his political career.

The group said the leafleting was aimed at sowing doubts among Republicans in the state about Romney’s conservative bona fides.

“It’s not that we were trying to portray him as a quote-unquote liberal, but to show that he’s flip-flopped on so many key issues,” American Bridge spokesman Ty Matsdorf said. “It’s highlighting his lack of core beliefs.”

Staff writer T.W. Farnam contributed to this report.