In a 3- or 3 1/2-quart slow cooker, combine turkey, ham, process cheese, cream cheese, mayonnaise, and mustard.
Cover and cook on high-heat setting for 1 to 2 hours or until cheeses are melted, stirring after 1 hour.
Serve immediately or keep warm, covered, on warm setting or low-heat setting for up to 2 hours, stirring occasionally. Before serving, stir in half of the bacon. Top with the remaining bacon and tomatoes.