Yeah, the Greens and the Libertarians have been short on wild enthusiasm for some time now. Arguably they need a rebranding (and arguably, the Tea Party is a Libertarian rebranding, for that matter--sort of, anyway).

Part of my argument, however--which is still not spelled out very well--is that if there are multiple 'insurgency' candidates that it may actually decrease turnout, because it's clear that the individual candidates' chances are compromised by the split.

The situation you're describing--in which TP support, or even a segment of it, becomes a prerequisite for nomination--is arguably concomitant to the TP supplanting the Republicans as a party, at least locally. (Granted, the phrase 'necessary, but not sufficient' should probably appear in here somewhere. :) )