CREATE TABLE table_18491 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

Name the minumim first elected for alvin bush
SELECT MIN("First elected") FROM table_18491 WHERE "Incumbent" = 'Alvin Bush'
SELECT MIN("First elected") FROM "table_18491" WHERE "Incumbent" = 'Alvin Bush'