By your logic, a Democrat staying home on election day, is a vote for Romney. It's illogical.
Our election system doesn't permit one to vote 'against' any candidate. All you can do is vote 'for' a candidate that suits you. If you abstain from voting, it doesn't increase the vote total of any candidate on the ballot.
If Romney is unable to convince or persuade enough people to vote for him, he simply loses because he didn't make the sale. It's that simple. Same holds for Obama.
See post #82.