CREATE TABLE table_18707 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

What was the last year that incumbent joseph t. deal was first elected?
SELECT MAX("First elected") FROM table_18707 WHERE "Incumbent" = 'Joseph T. Deal'
SELECT MAX("First elected") FROM "table_18707" WHERE "Incumbent" = 'Joseph T. Deal'