Isn't the Tea Party really doing everyone a favor in the long run by driving moderate republicans away?

All things are relative. This country has become completely irresponsible in spending. The Tea Party is a grassroots movement made up of your neighbors and mine. They want a return to sensible government, small government. Socialism is not the true center of the US but it may very well have gone so far that there is no where to go but toward communism because of a collapsed economy based on political power rather than common sense governing.