Libertarian Spoilers?

Markos thinks that Libertarians contributed to the Democratic sweep of Congress last November. He seems to be basing this assessment on the assumption that Libertarian candidates pull voters away from Republicans far more often than they do Democrats, a statement which is by no means self evident.

Take, for a random example, myself. I'm a little-'L' libertarian; the last time I voted for President I cast my vote for John Hagelin (it was awhile ago, youthful indiscretion and all). Presumably I'm the kind of person who might vote for a Libertarian candidate as, Markos notes, a protest vote.

But I don't think I've ever, ever, that I can recall, voted for a Republican. In a two-party race I'm almost certainly going to vote for a Democrat. The amount of pure, unadulturated crazy coming out of the Republican party is more than enough for me to overlook the Democrats' failings.

To be fair, Markos should list squeakers in the opposite direction as well i.e. those Republican victories where the margin was less that the number of Libertarian votes cast.