PM Kevin Rudd has defended Labor's latest round of attack adverts and vowed to keep on fighting as the latest opinion polls show the party heading for a heavy defeat at the September 7 election. A new Voice of Australia analysis reveals the Prime Minister has been trending down since he wrestled back the ALP leadership in late June. The latest analysis comes as bookmakers say Pauline Hanson's odds of winning a seat have been crunched, indicating she may have a serious chance.