Table schema:
CREATE TABLE table_13643320_2 (gtp_winning_team VARCHAR, circuit VARCHAR, gtu_winning_team VARCHAR)

Question: What was the GTP winning team in the round in Portland during which Jack Baldwin become part of the GTU winning team? 
SQL: SELECT gtp_winning_team FROM table_13643320_2 WHERE circuit = "Portland" AND gtu_winning_team = "Jack Baldwin"