Why are we so territorial?

I've wondered often why the LP folks down in US House District TX-14 (ie, Ron Paul's district) don't nominate him alongside the Republicans, instead of nominating their own guy (there's a thread at the TXLP forums where some guy freaks out about this.) Now there's a rut-ro in Arizona over whether some guy named Barry Hess, who's apparently quite popular, will run as a Libertarian or a Republican. Well, heck, let's nominate him and let the Republicans nominate him too, put "Libertarian/Republican" on the yard signs, and score an electoral victory. Sometimes I wonder how we claim to be the most rational party when we seem to demonstrate so little common sense.

UPDATE: Apparently neither Texas nor Arizona are "fusion states", whatever that means, so though I don't understand how any law could prevent us from nominating the same candidate as the Republicans, it seems it does.