Doubt it would be that bad. Would be 1964 worst case, and I think that's still pushing it. Maybe 1996.
Judging from the Republican primaries and if the Republican establishment will not sabotage his campaign, Ron Paul can carry all the traditional Republican (Blue) states (the lesser of the 2 evil arguments still can apply and the main stream Rep voters would go with Paul).
Besides that, Paul will carry Nevada, with a strong Libertarian leaning and very well organized base. Also, NH and VI would vote for Paul also, as shown in the Republican primaries. Even a district in Maine. Paul really is more accepted than the media and the establishment parties wants people to believe. I think if he had run against Obama, it would been an easy victory for the Republicans.
Don't worry, there's always Ron Paul 2024. It's inevitable.