If you are talking about third parties in general and not "Libertarians" in the strictest sense, I saw this coming last week:
"The very people who call Ron Paul advocates, “truthers”, “leftist loonies” and the like, will be the same people who after the election — if Obama wins — claim that Ron Paul people were really “Republicans who lost McCain the election” — never once noticing the absolute contradiction between those two claims."
I am speaking specifically about the Libertarian Party (of Texas), who had a deliberate plan to destroy good pro-taxpayer conservative Republicans and deliver seats to liberal Democrats in close elections.
Details about their plans were uncovered early in the election cycle:
http://travismonitor.blogspot.com/2008/07/libertarian-party-aspiring-to-be.html
The Libertarian Party, by pushing candidates in specific races were the Democrats ‘needed help’ to win - DELIVERED SEATS FOR SOCIALISTS.
I dont know how much the Texas Democrats paid the Texas LP to do what they did, or whether this was just stupidity on the part of the LP making a point, but I am beside myself that people on the side of freedom got shilled into supporting the LP, which in the end did nothing but help the Democrats.