If Cox is the nominee, the race will be a referendum on Richard Nixon and Watergate. He has no chance at all. Jeanine Pirro had a shot, but she blew it. I don't even expect her to win the AG race now.
As for John Spencer, I think he has very little chance. But he has the ability to attract media attention and rally the conservative base (not that large in NY). And maybe, just maybe, poll credibly enough to damage Hillary's chances of winning the White House in 2008.
its too bad the republicans can't find some celebrity candidate to run - ala Arnold. Hillary is more of a celebrity to the people who vote for her, rather then a politico.