CREATE TABLE table_28899 ("District" CLOB, "Incumbent" CLOB, "Party" CLOB, "First elected" CLOB, "Result" CLOB, "Candidates" CLOB)

How many times is the candidates charles f. mercer (f) 100%?
SELECT COUNT("Incumbent") FROM table_28899 WHERE "Candidates" = 'Charles F. Mercer (F) 100%'
SELECT COUNT("Incumbent") FROM "table_28899" WHERE "Candidates" = 'Charles F. Mercer (F) 100%'