South Australian Premier Jay Weatherill has taken responsibility for Labor's poor result in the Port Adelaide by-election.
Mr Weatherill says he takes responsibility for the slide of the safe Port Adelaide seat into marginal territory in one of two by-elections over the weekend.
Mr Weatherill, who took the reins from ousted former premier Mike Rann in October, said swings against third-term governments in by-elections were not unusual.
'It shows we've got a lot of work ahead of us to gain the support of some of our traditional supporters,' he told ABC radio on Monday.
'People take the opportunity to have a crack at the government knowing it's not going to change the government'.
With over 70 per cent of the vote counted on Monday, Labor's candidate for Port Adelaide, Susan Close, had 53 per cent of the two-party preferred vote, ahead of her nearest rival independent Gary Johanson, with 47 per cent.
Mr Rann's seat of Ramsay was won by Zoe Bettison, with 54.4 per cent of the primary vote.
Voters were choosing replacements for Mr Rann and his long-time former deputy Kevin Foley who announced their retirements last year.
Mr Foley's Port Adelaide seat was seen as a tough prospect for Dr Close, with strong independent competition.
Mr Weatherill admitted that changing the state government's premier and deputy last year was not an 'easy' exercise, suggesting the cabinet changes may have affected the by-election result.
Ramsay is in Adelaide's northern suburbs, centred on the Salisbury Council area and is solidly working class.
The biggest employer in the region is car maker Holden with the future of the manufacturer a key issue swaying voters to Labor, Mr Weatherill said.
'The future of Holden was a big issue on the minds of the workers out there. They obviously chose us to support them in that regard,' Mr Weatherill said.
