Ballot counting is still under way in the Adelaide eastern suburbs seat of Dunstan but early signs point to a historic loss for the 39-year-old Liberal leader.
With about one-third of votes still to be counted, Labor's Cressida O'Hanlon holds a 3.8 per cent two-party preferred lead over Liberal candidate Anna Finizio after a 4.4 per cent swing.
If confirmed, it would be the first time a South Australia opposition has lost a seat to the government in 116 years.
Mr Speirs acknowledged the disappointing result but said he wasn't going anywhere.
Liberal candidate Anna Finizio (centre) is trailing in her quest to win the seat of Dunstan in SA. (Jacob Shteyman/AAP PHOTOS)
"I have canvassed many of my colleagues over the last 48 hours ... and my colleagues were firmly supportive of me continuing in this role," he told ABC Radio on Monday.
But he said change was needed after the surprise swing.
"I can use this as a reason to take control of some things within the party," Mr Speirs said.Â
"To drive a different approach to perhaps the way the party is run and this should be a call to action for me and my team."
The party should consider emulating Labor's system of formalised factions as a more structured approach to organising, he said.
"I think there needs to be a level of rigour and discipline to the way that the different groups within the party operate," Mr Speirs said.
"Now, we haven't made a decision on that ... but it's something we should look at, because I look at the discipline of (Premier) Peter Malinauskas' party and the way it binds different groups together and I envy that."
Seated alongside his rival, Mr Malinauskas offered his diagnosis of the Liberal Party's woes.
"The Liberal Party's problem is that Alex Antic and the - I wouldn't say hardcores, I would say the radicals - have taken over the South Australian branch of the Liberal Party in a very material way," he said.
Senior Liberals, including SA Senator Simon Birmingham, voiced their support for fellow federal frontbencher Anne Ruston after she was deposed by Senator Antic for the top spot of the state's Senate ticket in a pre-selection stoush earlier in March.
"(Senator Antic) has managed to sign up all these people to the Liberal Party that have fundamentally different views to, what I suspect, even David holds," Mr Malinauskas said.
Both major parties suffered a fall in primary votes after a campaign defined by mud-slinging and personal attacks.
A potential swing to the Greens as a result of voter disillusionment was predicted in the lead-up to polling day and was borne out by an 8.8 per cent swing to candidate Katie McCusker.
"We should have countered that and we didn't do that. So that's something ... we need to do better," Mr Speirs said.
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