In much of today's world, socialism lacks the contentious overtones that it has in America.
The new French president, Francois Hollande, is a Socialist, and most of Western Europe adheres to socialist-style policies that endure under a variety of governing parties.
Canada, which resembles the U.S. in so many ways, has a universal health care system and its main opposition party, the New Democrats, is union-backed and has socialist roots.
One of the few contemporary U.S. politicians to embrace the socialist label is Sen. Bernie Sanders of Vermont. He formally lists himself as an independent, but throughout his career — including stints as a mayor and House member — he's described himself as a democratic socialist.
"Branding someone as a socialist has become the slur du jour by leading lights of the American right from Newt Gingrich to Rush Limbaugh," Sanders said in 2009. "If we could get beyond such nonsense, I think this country could use a good debate about what goes on here compared to places with a long social-democratic tradition like Sweden, Norway and Finland, where, by and large, the middle class has a far higher standard of living than we do."
The roots of socialism in America can be traced to the arrival of German immigrants in the 1850s, according to Rutgers University professor Norman Markowitz, who teaches the history of socialism and communism.
The Socialist Party of America grew significantly in the early 20th century under the leadership of union organizer Eugene V. Debs, electing a congressman and dozens of mayors. Debs ran for president five times, getting more than 913,000 votes in 1920 — the party's high-water mark. (At the time, Debs was in prison on charges that he had urged resistance to the draft during World War I.)
The party's following eroded during the 1920s, and Debs was succeeded as leader by Norman Thomas, a Presbyterian minister in New York. During the Great Depression, Thomas received 892,000 votes in the 1932 presidential election as Franklin Roosevelt won the first of his four victories.
After World War II, the anti-communist crusade led by Sen. Joseph McCarthy and the broader tensions of the Cold War relegated organized socialism in the U.S. to the political margins. The term "creeping socialism" emerged, used by conservatives to denigrate various policy proposals and initiatives that involved a role for the government.
After the Cold War's end, use of "socialist" as a political insult also receded. Markowitz believes its recent revival relates directly to the animosity toward Obama that is shared by a certain segment of Americans.
"There's this hysterical outbreak of abuse to prove that the president is not American, that he's a secret Muslim, that policies that past Republican administrations would have adopted are part of a socialist, communist conspiracy," Markowitz said.
Due in part to the multiple definitions of socialism, some conservatives wrestle with semantics as they seek appropriate terms for Obama's ideology.
"Instinctively, the president is a collectivist," said Ken Blackwell, former Ohio secretary of state and now a conservative commentator. "My fundamental belief is that he wants to transform our market economy into a government-controlled economy — not far afield from European-style socialism."
Steven Hayward, a resident scholar at the American Enterprise Institute and author of a two-volume biography of Ronald Reagan, said Obama is not a socialist under the strict definitions of that term — central economic planning and government control of production.
"However, socialism has a secondary meaning that is harder to explain — government regulations, supervision of the private economy," Hayward said. "The problem now with Obama is, 'What does he really think?'"
Ezra Klein, a blogger and columnist for The Washington Post, tackled the issue recently in a posting headlined "Barack Obama: Worst. Socialist. Ever."