user: Question: How many votes were cast when the constituency was Midlothian?
Columns: ['Constituency', 'Candidate', 'Affiliation', 'Votes -cast', 'Result - %', 'Loss/gain']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Glasgow South West', 'Tommy Sheridan', 'Solidarity (stood as Solidarity - TUSC)', 931.0, '2.9%', '-2.5%']
SQL:

assistant: SELECT SUM("Votes -cast") FROM "Table" WHERE "Constituency" = 'Midlothian';