Judge in 1998 child-support case called him a 'self-described religious zealot.'
Fetzer's remarks came after copies of D'Annunzio's court records were circulated among party officials in Raleigh and Washington.
D'Annunzio finished first in the May 4 primary. But his party has since gone to increasing lengths to portray him as unelectable.
"By my personal observation of his behavior, and by acquaintance with his record and background, I consider Mr. D'Annunzio unfit for public office at any level," said Fetzer. "What he could do to the party as our nominee is secondary in my view to what he could do to the country if he got elected. If he got elected, for crying out loud, that would be a disaster."
D'Annunzio, of Hoke County, faces fellow Republican Harold Johnson on June 22 in the 8th Congressional District runoff. The winner meets first-term incumbent Larry Kissell in November.
Court documents portray D'Annunzio as "a self-described religious zealot" who once called the U.S. government the Antichrist and told his ex-wife that he'd found the Ark of the Covenant.