What is the poll source when Jeff Sessions is at 58% and the date administered is July 31, 2008?
CREATE TABLE table_49513 (
    "Poll Source" text,
    "Dates administered" text,
    "Democrat: Vivian Davis Figures" text,
    "Republican: Jeff Sessions" text,
    "Lead Margin" real
)
SELECT "Poll Source" FROM table_49513 WHERE "Republican: Jeff Sessions" = '58%' AND "Dates administered" = 'july 31, 2008'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: What is the poll source when Jeff Sessions is at 58% and the date administered is July 31, 2008? ### Input: CREATE TABLE table_49513 (
    "Poll Source" text,
    "Dates administered" text,
    "Democrat: Vivian Davis Figures" text,
    "Republican: Jeff Sessions" text,
    "Lead Margin" real
) ### Response: SELECT "Poll Source" FROM table_49513 WHERE "Republican: Jeff Sessions" = '58%' AND "Dates administered" = 'july 31, 2008'