First of all, I agree with you that Cuccinelli is a decent candidate. If I were a Virginian, I would be supporting his candidacy too.
However, I disagree with your claim that "third parties just help the Democrats." I think that I can speak for a lot of third party voters in saying that the choice is often not between a 3d party protest vote and a liberal Republican nominee. The choice is between making a 3d party protest vote vs. staying home and not voting at all.
I'm disgusted by the arrogance of the RNC for acting that they somehow own my vote, and that somebody is "stealing" it. I don't owe them my vote, nor do you. They have to do something to earn it. Running candidates like Bush, Dole, Bush, McCain, and Romney does little to earn my vote, though in a couple of instances there (Romney 2012), I DID vote for the RINO candidate because the alternative was so bad. When the choice is between a RINO candidate and a Clinton-style mainline Democrat (as opposed to the hard left radical Obama, to me that's no choice at all.
However, I disagree with your claim that “third parties just help the Democrats.”
When has a 3rd Party candidate ever helped a Republican?
When has the “protest vote” EVER “sent a message” that made a POSITIVE difference for Conservatives?