What is the base spirit of the Huckleberry Mule?

The correct choice is 44 North huckleberry vodka because this spirit is specifically infused with huckleberry flavor, which is a key component of the Huckleberry Mule cocktail. This vodka enhances the drink's profile by adding a fruity and slightly sweet element that complements the other ingredients, typically ginger beer and lime juice. The use of huckleberry vodka aligns perfectly with the name of the cocktail, creating a signature experience that highlights this unique regional berry.

In contrast, while the other spirits listed can be used in various cocktails, they do not embody the specific essence of the Huckleberry Mule. Willie's Bighorn bourbon and Sauza Blanco tequila are distinct spirits that do not provide the intended flavor profile of huckleberry. Wildrye vodka, although a quality spirit, lacks the huckleberry infusion that is crucial to this particular cocktail, making 44 North huckleberry vodka the quintessential base spirit for the Huckleberry Mule.