Influx Insights posts about a branding study on the democratic hopefuls for 2008. Admittedly I haven't dug into the study yet. But it sounds interesting. According to Influx, "... it takes a look at the candidates as brands; examining awareness, qualities and perceptions."
Apparently Clinton is likened to a Volvo; Edwards to a Prius and Obama to a BMW Z4. I think Clinton is dead-on. I think of Edwards as more of a Mercedes station wagon. And Obama seems like a BMW 3-Series kind of guy [Z4 seems too flashy].