CREATE TABLE table_18626 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

In how many districts was the incumbent Estes Kefauver?
SELECT COUNT("District") FROM table_18626 WHERE "Incumbent" = 'Estes Kefauver'
SELECT COUNT("District") FROM "table_18626" WHERE "Incumbent" = 'Estes Kefauver'