Realistically, it depends on what state the voter is in. Voting for anyone in CA isn't going to matter. Ditto NY and probably two dozen other states.
The poster is in TN. TN didn't go for its native son Algore, if it's at risk of going Obama, it's been a landslide reelection.
I'd never recommend battleground (or Purple) state voters stay home in November. Go and hold your nose (if you must) once again: vote for the major GOP alternative to Obama and for the best candidates down the ballot.
Not if that candidate is Romney. I'm not a Republican. I'm a conservative.
/johnny