I would suspect that is about right for "likely voters", or real voters come next week, in Ohio. It's a big Union state, I'd actually not be too surprised if there weren't *more" than 45% Democrats in the final turnout.
In 2004 the exit poll found Ohio voters were
40% Pubbie
35% Rat
25% Indie
Where they are getting their projected turnout numbers, I have NO clue.