OK
But the voting reality is:
Bush 2004(reelection): 62 million votes (50.7%)
Romney 2012: 61 million votes (47.2%)
McCain 2008: 60 million votes (45.7%)
Indications are that conservatives declining to vote for a liberal Republican don’t really make a difference unless they vote for a noticeably popular third-party candidate.
The vote that swing that was larger was how many fewer votes Obama had in ‘12 than in ‘08, not how many fewer Romney had than McCain.
AS turnout varies and voter roles increase, percentages tell a story that is different than numbers.
You mention third party candidates but don’t really express your thoughts on them. Mine are that they undercut the chances of whatever side of the political spectrum spawns them.