Melt margarine in a large Dutch oven over medium-high heat. Add onion, carrot, celery, and ham; sauté 10 minutes. Add potato and broth; bring to a boil. Cover, reduce heat, and simmer 45 minutes or until potato is tender.
Place flour in a bowl. Gradually add milk, stirring with a whisk until blended. Add milk mixture, sage, salt, pepper, and nutmeg to soup; cook over medium-low heat 2 minutes. Add wine; cook 10 minutes or until thick. Garnish with sage, if desired.