user: Question: What is the Term Start date of the Progressive Party Prime Minister?
Columns: ['Name', 'Born-Died', 'Term start', 'Term end', 'Political Party']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Prime Ministers 1914 - 1925', 'Prime Ministers 1914 - 1925', 'Prime Ministers 1914 - 1925', 'Prime Ministers 1914 - 1925', 'Prime Ministers 1914 - 1925']
SQL:

assistant: SELECT "Term start" FROM "Table" WHERE "Political Party" = 'Progressive Party';