I will never vote for romney.
Never!
Nor will I.
Ditto.
If the two main choices are Obama and Romney will you join me in voting for the Green Party candidate?
There is a chance that there will be a sufficient number of liberals upset by Obama that 5% of the vote could go to the Greens. If that happens then all sorts of things kick in, like their candidates being allowed into debates, etc.
Going directly at the Democrats with the Republicans doesn't seem to have worked that well to date. A pincer movement involving a left-flanking Green Party might just do the trick!