Former foreign minister Alexander Downer is set to become new president of the South Australian Liberal Party.

He told ABC radio on Tuesday that when the nominations closed he was the only candidate, but the appointment has to be confirmed on October 19 at the party's annual general meeting.

He will replace Grant Chapman, whose maximum three-year term will expire soon.

The next South Australian election will be held in March and Mr Downer said the party could not afford to be complacent in its bid to win power from the ALP.

"It will be a tough election and campaign," he said.

Mr Downer said the Liberals had to make sure they campaigned on the ground at a grass-roots level, rather than just concentrating on a state-wide campaign.