I saw an interview with John Fund today. I don't always agree with him but today I did.Probably the requirement to have 400 signatures from each of their 11 congressional districts.
The Republicans and the Democrats both make such an effort to exclude 3rd party candidates, independents and libertarians mostly, that sometimes they make it difficult for their own.
In this case, the rules designed to exclude 3rd party candidates seems to have tripped up Newt Gingrich and Rick Perry alike.
Newt declared that he would immediately begin a write in campaign.
Unfortunately, the state of VA doesn't allow write in votes.