I was up in DC this weekend. Saw millions of Obama stickers.
My buddy who is a Dem., not a lib, but a dem because his father was etc... He is very nervous about both the candidates. He was shocked that they decided on the two of the most unlikable ultra-leftists. I told him that McCain ain’t exactly a conservative.
This is my selling point when I talk to democrats about the election. A lot of them don't like either candidate, so right there one has a foot in the door. I gently point out that McCain infuriates the right, that he has always reached across the aisle to compromise and work with Democrats, that there are rumors he once considered becoming a Democrat (untrue, I think, but no harm in pointing out the rumor to a Democrat!), and that his social positions are centrist at best, liberal at worst. I say he is the ideal candidate for them: he'll defend the country but has liberal social positions. In other words, sell McCain as a closeted Democrat.
This approach appears to be making some inroads with Democrat coworkers and neighbors in one of the most liberal counties in the US. Try it, it might work for you.