Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What was the smallest lead margin when the source of polls came from Strategic Vision and Democrat Carl Levin had 57%?

### Inputs:
table_name: table, columns: ['Poll Source', 'Dates administered', 'Democrat: Carl Levin', 'Republican: Jack Hoogendyk', 'Lead Margin']

### Response:
SELECT MIN Lead Margin FROM table WHERE Poll Source = Strategic Vision AND Democrat: Carl Levin = 57%