user: Question: What is the d-r spread if the no party preference is 31.8%?
Columns: ['City', 'Population', 'Registered voters', 'Democratic', 'Republican', 'D–R spread', 'Other', 'No party preference']
Types: ['text', 'real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Campbell', 39108.0, '53.4%', '45.3%', '23.8%', '+21.5%', '7.3%', '26.2%']
SQL:

assistant: SELECT "D–R spread" FROM "Table" WHERE "No party preference" = '31.8%';