they actually were partisan political groups and probably shouldn't have been claiming they weren't for tax exemption purposes. Part of that bias, though, comes from the word "party" being right in the name of some of these groups--and I think when we hear Republican politicians, like, for example, Michele Bachmann, describe themselves as "Tea Party" conservatives, it only adds to the misunderstanding. But I do seem to recall some blather back in 2009-2010 that the Tea Party wasn't supposed to be about conservative or liberal politics, per se, even though the movement is credited with getting an awful lot of Republicans elected in the 2010 congressional elections.
But to clarify, when the term "Tea Party" is being used, a distinction should be made between a "political party"--the thing where like-minded individuals work on getting particular candidates elected, and the more loose kind of party, where people wear silly hats. Lines have clearly been blurred, people. If only the IRS questionnaires asked fewer questions about what these groups did, and just concentrated on the hats, things would obviously be different.