There are serious drawbacks to instant runoff voting that you should take the time to understand. I was a fan of it until I read more about it here:
Once I read that book, I realized that there are potentially ruinous pitfalls associated with every known voting system.
I keep seeing libertarians push IRV but every country with IRV still has a two-party-dominant system. The link that dkinmn posted perhaps explains why.
If you really want to fix the problem, go for range voting, or at least approval voting.
For an engaging in-depth look at the properties of various voting systems, read Gaming the Vote by William Poundstone.