(CNN) - In framing his attacks on President Barack Obama for a possible November showdown, Newt Gingrich repeatedly brings up the name of an influential radical organizer from the first half of the 20th century.
"Saul Alinsky radicalism is at the heart of Obama," Gingrich said Sunday in an interview with CNN Chief Political Correspondent Candy Crowley.
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The night before, the former House Speaker invoked the name in his victory speech after the South Carolina primary, saying: "The centerpiece of this campaign, I believe, is American exceptionalism versus the radicalism of Saul Alinsky."
And earlier, at a New Year's Eve campaign event in Iowa, Gingrich declared that Obama "really is sort of a classic Saul Alinsky radical whose basic ideas are the opposite of what we need to create jobs."
So who is Saul Alinsky, and why is Gingrich so insistent on linking that name to Obama?
Born in Chicago in 1909, Alinsky organized communities in his birth city and California, helping minorities in poor neighborhoods exert political force by collectively demanding better working conditions and getting them to polling stations.
Alinsky's most famous book, "Rules for Radicals: A Pragmatic Primer for Realistic Radicals," describes a confrontational method for curing economic inequality - something most conservatives would shun.
In reference to "The Prince" by Niccolo Machiavelli, the 16th century primer for political intrigue, Alinsky wrote: "'The Prince' was written by Machiavelli for the Haves on how to hold power. 'Rules for Radicals' is written for the Have-Nots on how to take it away."
Alinsky further explained his methods in a video clip included in the 1999 documentary "The Democratic Promise: Saul Alinsky and his Legacy."
"First rule of change is controversy," Alinsky said. "You can't get away from it for the simple reason all issues are controversial. Change means movement and movement means friction, and friction means heat, and heat means controversy."
Democrats have long been aligned with Alinsky's name and methods, even if they haven't always trumpeted his legacy.
Secretary of State Hillary Clinton wrote her undergraduate college thesis on Alinsky, a fact critics used to paint her as a radical during her tenure as First Lady and later when she ran for the 2008 Democratic nomination.
Obama, who was 10 years old when Alinsky died in 1972, has never publicly said he was influenced by Alinksy's teachings. However, he worked as a community organizer in Chicago in the 1980s, when colleagues of Alinsky would still have been active.
Conservatives also have cited Alinsky as an influence, in technique if not in substance.
In an interview with the Financial Times in 2009, former Republican House Majority Leader Dick Armey said conservatives fed up with Obama's policies could employ Alinsky's practices.
"What I think of Alinsky is that he was very good at what he did, but what he did was not good," Armey said.
Now the leader of Freedomworks, a conservative organization aligned with the tea party movement, Armey acknowledged some Alinsky-esque activities by the right-wing group.
"We don't organize people to turn up at these town-hall meetings – we don't provide buses to get them there," he told the newspaper. "But we tell them about the meetings and we suggest good questions they could ask."