This means that antiwar activists and civil libertarians are caught in an odd bind: many of them are genuinely appalled by Obama’s continuation of Bush-era security policies on detention and surveillance (and especially by his outrageous new claim of assassination powers), they are disgusted that his administration is hiding behind the state secrets privilege to cover up for the Bush administration, and they object to escalating the war in Afghanistan. However, they know very well that the alternative to Obama is to have all of these things, plus torture, aggressive foreign policy in all directions, and possibly war with Iran.
For all the various disagreements I have with the Democratic party, I don't have anywhere to turn. The Republican party is worse on gay rights, worse on civil liberties, worse on deficits, and worse on Afghanistan. I could vote Green or other third party, but they don't have a chance, and I'm increasing the chance that the Republican could win by "throwing away" my vote.
On a more local scale, this also happened in the recent Minnesota gubernatorial elections. I had no love for the DFL candidate, Mark Dayton, and considered voting for Tom Horner, the Independence party candidate. But the thought that my wasted vote could have allowed uber-conservative GOP candidate Tom Emmer to win meant holding my nose and voting for Dayton. As it turns out, the election was fairly close, so I'm glad I did.
However, with instant runoff voting, I could have voted for Horner and still had my vote count for Dayton when he failed to garner a substantial number of votes. In 2000, liberals could have voted for Ralph Nader without helping George W Bush win. I could vote for a candidate with better civil libertarian bona fides in 2012 while not being an accessory to the ascension of President Palin.
Now, chances are this wouldn't actually give rise to a multi-party system with loads of parties, a la proportional representation. But it would at least give me the option to lodge a protest vote without feeling like I'm aiding candidates who are anathema to my every policy preference.
(As a side note, liberals are nowhere near as good as conservatives at scaring the shit out of incumbent senators with primary challenges. The latest victim is Olympia Snow.)