Coat slow-cooker bowl with nonstick cooking spray. Add crushed tomatoes, whole tomatoes, red wine, juice from 1 can of clams, onion, red pepper, garlic, sugar, oregano, salt and cayenne. Break up tomatoes with a wooden spoon.
Cover and cook on HIGH for 6 hours or LOW for 8 hours.
Thirty minutes before end of cooking time, stir in shrimp, scallops and drained clams. Just before serving, stir in parsley. Serve with sourdough bread, if desired.
