How do they manage to do this? Because Democrats ceded the field. Above all, they do not understand language. Their initiatives are posed in impenetrable policy-speak: the Patient Protection and Affordable Care Act. The what? - can anyone even remember it? No wonder the pejorative "Obamacare" won out. Contrast that with the Republicans' Patriot Act. You're a patriot, aren't you? Does anyone at the GED level have a clue what a Stimulus Bill is supposed to be? Why didn't the White House call it the Jobs Bill and keep pounding on that theme?
The media are also complicit in this phenomenon. Ever since the bifurcation of electronic media into a more or less respectable "hard news" segment and a rabidly ideological talk radio and cable TV political propaganda arm, the "respectable" media have been terrified of any criticism for perceived bias. Hence, they hew to the practice of false evenhandedness. Paul Krugman has skewered this tactic as being the "centrist cop-out." "I joked long ago," he says, "that if one party declared that the earth was flat, the headlines would read 'Views Differ on Shape of Planet.'"
But really, you gotta read the whole thing. You can check it out here.