user: Question: In 1955 which party did Thomas Mitchell belong to?
Columns: ['Candidate', 'Party', 'Constituency', 'Year', 'Days']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Alfred Dobbs', 'Labour', 'Smethwick', '1945', '1 1']
SQL:

assistant: SELECT "Party" FROM "Table" WHERE "Year" = '1955' AND "Candidate" = 'Thomas Mitchell';