1. In a 5- to 6-quart pan over high heat, stir oil, onion, and garlic until onion is limp, about 5 minutes. Add chili powder and stir just until fragrant, about 30 seconds. Add broth, cover, and bring to a boil.
2. Cut potatoes into 1/2-inch cubes.
3. Add potatoes to boiling broth. Cover and return to a boil, then reduce heat and simmer until potatoes are tender when pierced, about 10 minutes.
4. Add tomatoes with juice, chili, corn, peas, and clams with juice, stirring to mix. Turn heat to high, cover, and return to a boil.
5. Add lime juice, hot sauce, cilantro, and salt and pepper to taste. Ladle soup into bowls.