Heat the oil in a large saucepan over medium heat. Add the chili powder, garlic, onion, chipotle and 1 teaspoon salt and cook, stirring, until the onion softens, about 5 minutes. Add the turkey stock, tomatoes, 1/2 cup water and half the tortilla chips, bring to a boil, reduce the heat slightly and simmer, uncovered, until the soup has reduced slightly, about 25 minutes. Add the corn and cook for 5 minutes more.
Remove from the heat and stir in the turkey and lime juice. Adjust the seasoning with salt, if needed. Divide the soup among 4 bowls. Top with the cheese, cilantro, the remaining tortilla chips and avocado if using.
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