CREATE TABLE table_21577 ("County" TEXT, "Kerry%" TEXT, "Kerry#" FLOAT, "Bush%" TEXT, "Bush#" FLOAT, "Others%" TEXT, "Others#" FLOAT)

Name the minimum kerry # for bush % for 50.9%
SELECT MIN("Kerry#") FROM table_21577 WHERE "Bush%" = '50.9%'
SELECT MIN("Kerry#") FROM "table_21577" WHERE "Bush%" = '50.9%'