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

### Instruction:
What is the largest lead margin when Schweitzer has 55% and Jones is not an option?

### Inputs:
table_name: table, columns: ['Poll Source', 'Dates administered', 'Democrat: Brian Schweitzer', 'Republican: Roy Brown', 'Libertarian: Stan Jones', 'Lead Margin']

### Response:
SELECT MAX Lead Margin FROM table WHERE Democrat: Brian Schweitzer = 55% AND Libertarian: Stan Jones = not an option