... A "Tea Party" third party would pretty much be a sap on the GOP, resulting in either a moderate Republican Party or Democratic dominance. I see room for a moderate/classical liberal party ala the Minnesota Independence Party, which I would love to see in general, but only because it would be able to find room and balance in the middle. But as much as I'm a pro-third party guy, I would sooner want a change in the electoral system than for a single third party to come to prominence.
The Tea Party is just a third force for neo-liberalism. The missing party is a socialist/social democrat voice in the US, and it will never be allowed.