CREATE TABLE table_18492 ("District" CLOB, "Incumbent" CLOB, "Party" CLOB, "First elected" FLOAT, "Result" CLOB, "Candidates" CLOB)

What is the incumbent for pennsylvania 15
SELECT "Incumbent" FROM table_18492 WHERE "District" = 'Pennsylvania 15'
SELECT "Incumbent" FROM "table_18492" WHERE "District" = 'Pennsylvania 15'