What is the best way to introduce a new cat to a household where the resident cat may feel threatened and chased by the new arrival?

The best way to introduce a new cat to a household where the resident cat may feel threatened is to gradually introduce them by keeping them in separate rooms at first, allowing them to smell each other's scents before any direct contact. Slowly allow supervised interactions and provide plenty of resources like food, water, and litter boxes to prevent competition. Patience and positive reinforcement are key to helping the cats adjust to each other.