We have open primaries here (VA) and it can work both ways. Another influence is to send your usual political donation directly to the conservative candidate of your choice, and not let it be filtered through the NRCC etc. I maintain that the TP is a very useful and highly effective tool - the sheer number of like-minded people the TP has energized is awesome. The Dems know this, and it is scaring them witless. Witness their scornful derision - a sure sign that they are stung.
Amen. Nothing worse than watching your money being sent to Scozzafava in NY-23 recently; or the likes of Collins or Snowe in Maine.