The cream cheese and mayo are essential for a deliciously creamy base, I wouldn't recommend skipping either of these ingredients. You can, however, substitute the mayo with sour cream. If preferred, you can swap the thousand island dressing with Russian dressing.
I recommend shredding the Swiss cheese yourself as the pre-bagged variety contains anti-caking agents which prevent it from melting as well. Feel free to substitute the Swiss cheese with mozzarella if you'd like.
Serve with cocktail rye bread, rye chips, crackers, tortilla chips, celery and other crunchy vegetables.
This dip is easily made in the crockpot. I would recommend a small 4 qt slow cooker or to double the recipe for a larger crockpot. Place all the ingredients into the slow cooker and cook on high for 1 hour or on low for 2-3 hours. Give it a stir or two throughout the cooking process to avoid it burning on the bottom of the slow cooker.