CREATE TABLE table_18253 ("District" CLOB, "Incumbent" CLOB, "Party" CLOB, "First elected" FLOAT, "Result" CLOB, "Candidates" CLOB)

what's party with district being pennsylvania 21
SELECT "Party" FROM table_18253 WHERE "District" = 'Pennsylvania 21'
SELECT "Party" FROM "table_18253" WHERE "District" = 'Pennsylvania 21'