user: Question: What is the percentage of registered voters in which the d-r spread is +10.4%?
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: ['Carlsbad', 102342.0, '64.7%', '28.0%', '42.0%', '-14.0%', '8.5%', '24.9%']
SQL:

assistant: SELECT "Registered voters" FROM "Table" WHERE "D–R spread" = '+10.4%';