CREATE TABLE table_18312 ("District" CLOB, "Incumbent" CLOB, "Party" CLOB, "First elected" FLOAT, "Result" CLOB, "Candidates" CLOB)

How many sitting politicians were originally elected in 1972?
SELECT COUNT("Incumbent") FROM table_18312 WHERE "First elected" = '1972'
SELECT COUNT("Incumbent") FROM "table_18312" WHERE "First elected" = '1972'