The S word: A Short History of an American Tradition... Socialism, by John Nichols.
Here's the blurb from Amazon:
A few months before the 2010 midterms, Newt Gingrich described the socialist infiltration of American government and media as “even more disturbing than the threats from foreign terrorists.” John Nichols offers an unapologetic retort to the return of red-baiting in American political life—arguing that socialism has a long, proud, American history. Tom Paine was enamored of early socialists, Horace Greeley employed Karl Marx as a correspondent, and Helen Keller was an avowed socialist. The “S” Word gives Americans back a crucial aspect of their past and makes a forthright case for socialist ideas today.