Preheat the oven to 325 degrees F (165 degrees C). Grease and flour a 10-inch Bundt pan.

Sift flour, baking powder, cinnamon, cloves, nutmeg, and salt together into a bowl.

Cream sugar and shortening in a large bowl with an electric mixer until light and fluffy. Add eggs, one at a time, beating well after each addition. Mix in flour mixture alternately with mashed potatoes and milk. Stir in walnuts and raisins. Pour batter into the prepared pan.

Bake in the preheated oven until a toothpick inserted into the center comes out clean, 1 1/2 to 2 hours.