“His campaign manager simply believed that as the frontrunner, Reagan was above the debate.”
So, same for Trump’s campaign manager. Trump is in the same position as was Reagan. There is absolutely NO REASON for him to participate, particularly given the liklihood that it’s a setup by Fox to try and trash him. He only looses by attending. There just isn’t any upside for him.
Reagan lost Iowa, despite almost being a native son (i.e. being from neighboring IL). He never skipped another debate after that. Bush skipped the NH debate over the debate arrangements (he was sandbagged by having to debate four other candidates instead of just Reagan, as had previously been arranged via bilateral discussions) and lost the NH primary by a country mile, despite being a near native son (i.e. being from neighboring MA). The common thread is that skipping debates - for whatever reason - used to mean losing states. Maybe Trump will prove the exception.