Wins more important than swing: SA Premier

Labor's victory in two by-elections is more important than the swings against the party, South Australian Premier Jay Weatherill says.

Mr Weatherill says he took responsibility for the safe Port Adelaide seat's slide into marginal territory in one of two by-elections on the weekend.

But he said the wins in the seats of Port Adelaide and Ramsay showed voters had warmed to Labor's new leader, who took over from former premier Mike Rann in October.

"There was every opportunity with the community ... to send us a very clear message on how unhappy they've been in the past and many chose to," he told journalists on Monday.

"But many others said `we like the early signs and we're prepared to give you a go'."

Mr Weatherill earlier this morning said swings against third-term governments in by-elections were not unusual.

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 a change of leadership was not an "easy" exercise, suggesting the cabinet changes may have affected the by-election result.

While transitioning to a new leadership could be disorderly and disruptive, the voters had shown confidence in the new government, Mr Weatherill said.

"Of course there are many people who have reservations about the government (and) me, but a majority of people in these elections voted Labor," he said.

Ramsay is in Adelaide's northern suburbs and solidly working class.

The biggest employer in the region is car maker Holden, and the future of the manufacturer was a key issue swaying voters to Labor, Mr Weatherill said.