First off, has it occurred to you that you're arguing that those voters should have voted against their consciences? That you put your partisan ambitions above the free choice of other people?
Second, were you aware that the Libertarian Senate candidate in South Dakota withdrew from the race several weeks ago, and publicly threw his support to John Thune? Well, a lot of South Dakotan voters weren't aware of it either -- because the regional media barely mentioned it!
Third, why do you think that those 3000 LP voters would have voted Republican had there been no LP candidate? What about the possibility that they would have voted "None Of The Above Is Acceptable" in the only available way -- by staying home?
If you want Republican candidates to garner the votes that ordinarily go to minor-party candidates, you have to offer those voters what they want. What minor-party voters tend to want is ironclad pledges of allegiance to particular principles (e.g., Libertarian), or particular stands on issues (e.g., Right To Life). To make such pledges entails the risk of alienating other voters who would normally vote Republican.
Where I live (Long Island, NY), Republicans are just "Democrats On A Budget." They never dissent from any Democratic statist initiative; they just promise to phase it in or do it cheaper. Since that contradicts my beliefs, I stay home. A great many voters do the same; we just want real limited-government Constitutional-fidelity Republicans, and all we get are fakers.
In short, it's time you stopped assuming that your troubles were caused by the minor parties. You don't have any claim on those votes -- and the people who cast them would be the first to tell you so. Get to work on getting the GOP's house in order if you want better results.
Freedom, Wealth, and Peace,
Francis W. Porretto
Visit the Palace Of Reason: http://palaceofreason.com
Incidentally, since it's still a relatively free country, I am still free to advocate always voting against Democrats as effectively as possible. This is almost never accomplished by voting third party--