CREATE TABLE table_18161 ("District" CLOB, "Incumbent" CLOB, "Party" CLOB, "First elected" CLOB, "Results" CLOB, "Candidates" CLOB)

Incumbent Tim Holden belonged to what party?
SELECT "Party" FROM table_18161 WHERE "Incumbent" = 'Tim Holden'
SELECT "Party" FROM "table_18161" WHERE "Incumbent" = 'Tim Holden'