Glenn Reynolds sees the value in third parties, by keeping the extremists from prevailing:
this is how third parties traditionally have an impact -- by costing one of the two major parties close elections.
As Thomas Sowell put it, the GOP offers (mostly) second-rate firemen to protect my liberties, and the Democrat party (mostly) first-rate arsonists who would burn those liberties down. Having the second-rate firemen firmly in charge, with a majority capable of cloture over a filibuster, can be just as bad as having the arsonists in charge by just one seat.
Anyone from the Dems or the "moderate" GOP who appreciates the valuable service we Libertarians provide in keeping the even keel, please donate to one of the charities in the ribbon to the right, or to the LP itself. In a way we keep you guys from looking worse than you would, even without getting our own people into office.
What would really fix this problem, though, would be a return to the original State appointment (and State recall) of Senators, instead of directly electing them. But Libertarians would still have the Governorships to regulate.