The party which has the second largest number of parliamentarians is confronting the resurgent popularity of the ruling African National Congress (ANC) party since President Cyril Ramaphosa took office -- dubbed "Ramaphoria".
"We have reaffirmed that our purpose as Democrats is not to fight for a better behaved ANC, but for an entirely new government for South Africa, led by us and our values," he said to a packed audience in Pretoria on the last day of the conference.
"So let us go forward with confidence and vigour to pursue our goals for the 2019 elections."
Maimane, who was elected unopposed, said that party's main electoral goal was to take control of Gauteng province, the country's economic powerhouse that includes the capital Pretoria and commercial hub Johannesburg.
"We can do it, and we will do it," he said to cheering.
The party has faced several crises in recent months including a bruising public spat between the leadership and the mayor of Cape Town Patricia De Lille, controversial tweets by former leader Helen Zille and the breakdown of a coalition partnership.
The radical Economic Freedom Fighters (EFF) party, which had supported the DA's minority administration in Port Elizabeth, turned against the party, withdrawing its support over the DA's position on land reform.
The ANC announced at the end of last year that it would seek to amend the constitution to allow for land to be "expropriated without compensation" to address the legacy of colonialism and apartheid.
It is widely understood that the policy will mean transferring land from white land owners to members of the disadvantaged black majority.
The DA has opposed the changes which were enthusiastically welcomed by the EFF.
"Everyone should have the dignity of a home, the dignity of land and, most critically, the know-how," Maimane said on Sunday. "We don't need to change our precious constitution for this -- we just need to cut corruption and get the job done properly."
President Ramamphosa, who in February succeeded unpopular former president Jacob Zuma who was widely seen as boosting support for opposition parties, has increased the ANC's appeal with voters and business.
There has been speculation that Ramaphosa could go to the country before the ANC's term in office expires in 2019.
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