TAMPA, Florida — A casual observer on the Republican campaign trail could be forgiven for thinking President Barack Obama has traded in his American flag lapel pin for one with a hammer and sickle.

To some rightwing Republicans the US leader is a rabid socialist, to others, he's a card-carrying Marxist. But to most, mention the name "Obama" and they see red.

On the eve of Tuesday's primary elections, one of the loudest battle cries is that the incumbent Democratic president will bring America to ruin -- unless a conservative Republican is elected to replace him in November.

Former House speaker Newt Gingrich tried to convince voters late Saturday that he was just such a man, telling supporters at a rally in Palm Beach that unlike Obama he would run an "American campaign" for the presidency.

"I am for the Declaration of Independence," Gingrich proudly proclaimed. "I am for the Constitution."

Obama, by contrast, "is for European Socialism," the Georgia lawmaker said.

Frontrunner Mitt Romney also has been fond of telling his supporters here that Obama is a modern-day Red Menace, warning in a speech this weekend that the president "wants us to turn into a European-style welfare state."

That fate, Romney said, would "poison the very spirit of America."

Even former White House hopeful Michele Bachmann -- who earlier this month abandoned her White House campaign -- took to the airways this weekend to predict the imminent demise of what she described as a radical Obama administration.

"Obama will be a one-termer, because all he has been about is redistribution of wealth and the rise of socialist principles," said Bachmann said in an appearance Sunday on US television.

Florida is a key battleground in the November election, as Republicans vie for their party's presidential nomination amid the hope of turning Obama into a one-term president.

Fears of a Communist scourge are deeply rooted in the American psyche, dating back to the "red scare" at start of the Cold War over half a century ago -- when thousands of Americans were accused of being Communist sympathizers, and many were persecuted, banned from working and in some cases forced to move abroad.

And little distinction is drawn in the United States between the ideological positions of Socialism and Communism.

Now in a time of economic uncertainty and political upheaval, such sentiments are finding some breathing room again.

A recent poll by the Pew Research Center found 60 percent of Americans respond negatively to the term "socialism."

In a Republican debate in New Hampshire earlier this month, Texas Governor Rick Perry was adamant that Obama is a socialist. "I make a very proud statement and a fact that we have a president that's a socialist," he said.

"I disagree with (the) premise that somehow or another President Obama reflects our founding fathers. He doesn't. He talks about having a more powerful, more centralized, more consuming and costly federal government," he said.

Back in Florida, at a campaign event at the Aloma Baptist Church in Winter Park, Niels Lobo said he appreciated the marked anti-socialist tenor of Gingrich's remarks.

Lobo, a professor of computer sciences at the University of Central Florida, said he is eager to see Obama voted out "because he is a Marxist."

"We really want him out," he said. "He is slowly driving the country towards Marxism."

Lobo added he takes particular exception to the president's landmark healthcare reform plan which comes a bit too close for his taste to socialized medicine. "'Obamacare' needs to be killed," he argued.

Tina Altic, another Gingrich supporter said she was backing the Georgia lawmaker because he was best able to turn back Obama, whom she accused of "running this country into the ground."

Obama has also run foul of many conservatives for being too deferential toward foreign leaders, they say.

"At least he won't apologize for the country and he will stop the spending," the 66-year-old retiree said of Gingrich at an Orlando rally.

Another Gingrich supporter, John, who only gave his first name, said he was convinced Obama's upbringing overseas -- he spent part of his childhood in Indonesia -- explains his alleged estrangement from centrist American values.

"Mom, baseball and apple pie," he said, citing what many think are the holy trio of American values -- something missing from Obama's world view. "He doesn't understand us," said John.