I think the only Republican who would have had a decent chance to win against Pryor would have been Mike Huckabee if he dropped out of the 2008 GOP primary race earlier like for example in mid or late February 2008 when we all knew that John McCain was going to win the Republican nomination and as the candidate filing deadline in Arkansas is usually early March (when McCain officially clinched the nomination after winning in Ohio, Texas, Rhode Island and Vermont).
Even Huckabee would have been a long shot against Pryor that year imo