CREATE TABLE table_18617 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" TEXT, "Result" TEXT, "Candidates" TEXT)

what's the incumbent with result being new seat republican gain
SELECT "Incumbent" FROM table_18617 WHERE "Result" = 'New seat Republican gain'
SELECT "Incumbent" FROM "table_18617" WHERE "Result" = 'New seat Republican gain'