CREATE TABLE table_18158 ("District" CLOB, "Incumbent" CLOB, "Party" CLOB, "First elected" CLOB, "Results" CLOB, "Candidates" CLOB)

How many incumbents were first elected in 1984?
SELECT COUNT("Incumbent") FROM table_18158 WHERE "First elected" = '1984'
SELECT COUNT("Incumbent") FROM "table_18158" WHERE "First elected" = '1984'