CREATE TABLE table_18283 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

To which party does Robert W. Edgar belong?
SELECT "Party" FROM table_18283 WHERE "Incumbent" = 'Robert W. Edgar'
SELECT "Party" FROM "table_18283" WHERE "Incumbent" = 'Robert W. Edgar'