[ZenGum]

Australia also has full preferential voting, as described by Rhianne. It works and is pretty easy if you're choosing from no more than 10 or so, but for some elections (proportional representation in the upper house) there can be 50 or 100 candidates. For this we let people either vote their preferences all the way through, or give their whole vote to a single candidate (party) and let that candidate assign the preferences as they like. This is simpler for the voters and gives minor parties who don't get elected the chance to influence those who do, ask for questions to be put in the house, et cetera. Preference dealing can slide into political shennanigans, tho.

This system returns about 5 - 10% invalid votes, but because voting is compulsory in Australia, quiet a few of those are probably deliberate.

I think adopting this would do the USA good, because it prevents the dilemma of "if I don't vote for a major party, the wrong major party might get in". People could vote for Perot, and then give their preference to Gore, for example. It might loosen up the power duopoly you guys have.