The President of South Australia's Legislative Council has been chosen to replace Cory Bernardi in the Senate.

Key points: Cory Bernardi defected from the Liberals to start his own party in 2017

Cory Bernardi defected from the Liberals to start his own party in 2017 He formally quit Federal Parliament in January

He formally quit Federal Parliament in January The Liberal Party has voted for SA Upper House President Andrew McLachlan to replace him

In a win for the state's moderate Liberals, Andrew McLachlan is set to fill the vacancy created by Mr Bernardi.

Mr Bernardi defected from the Liberal Party in 2017 to set up the Australian Conservatives.

He announced his resignation last year after claiming he had achieved his goal of moving the party further to the right with Scott Morrison replacing Malcolm Turnbull as Prime Minister.

Mr McLachlan, 54, beat out contenders lawyer Morry Bailes and business consultant Michael Van Dissel in a vote in Adelaide this morning.

Mr McLachlan was first elected to the South Australian Parliament's Upper House in 2014 and became President in 2018.

"I am honoured to be selected as the new Liberal senator for South Australia and am looking forward to getting to work within the Morrison Liberal Government team," he said after the vote.

"I understand the importance of this new role and I am eager to draw on my experience to work with South Australians and businesses to help drive a strong economy and a better future for our state."

Mr McLachlan worked as a lawyer and in finance before becoming a politician.

He is a Colonel in the Army Reserve and served in Afghanistan, earning a Conspicuous Service Cross in 2007.

The SA Upper House vacancy will be filled through a preselection process conducted by the Liberal Party in March.

Run of difficulties for conservatives

Cory Bernardi first joined the Senate in 2006. ( ABC News: Nick Haggarty )

Mr Bernardi announced in June that a "lack of political success" and money had meant he was deregistering the Australian Conservatives.

The South Australian's Liberal colleagues were furious at his decision to break away from the party just after the 2016 Federal Election, when he secured a six-year term.

His factional foe Simon Birmingham, who spoke next to Mr McLachlan after his win today, described it as a "dog act".

Mr McLachlan today assured his colleagues he would not be following in Mr Bernardi's footsteps and would stay in the Liberal Party throughout his time in the Senate.

"As a new newly minted senator, perhaps next week, I'm planning to avoid controversy as you can understand — and just work hard," he said.

Shortly after forming, the Australian Conservatives merged with Family First. In doing so, the party gained two representatives in the South Australian Upper House.

One of those members failed to get re-elected at the 2018 state election, and the other defected to the Liberal Party in the days following the disappointing showing at the ballot box.