What if Pat Buchanan didn't make the "culture war" speech at the 1992 GOP convention?
[2000 election between Bush and Gore as example]
" . . . As a consequence, and we elaborate on this later, the 60% figure we have noted above is an upper bound: at most 60% of Nader voters would have voted for Gore had they faced a two-candidate election, and at least 40% of the would have chosen Bush. . . "
http://www.sscnet.ucla.edu/polisci/faculty/lewis/pdf/greenreform9.pdf