Heat large skillet over medium heat. Add mushrooms, onion and sausage; cook and stir 8 minutes or until onion is softened. Remove to Crockpot™ slow cooker.
Add tomato sauce, wine and vermouth to Crockpot™ slow cooker. Cover; cook on LOW 6 to 7 hours or on HIGH 31/2 to 4 hours. Add clams; cover and cook on HIGH 10 to 15 minutes or until clams open. Discard any clams that do not open. Serve over pasta and with bread, if desired.