Baselines and biases: The trouble with opinion polls in race to the local elections

The election period has arrived, and it is bumper season for opinion researchers.

While the utility of the polling industry cannot be underestimated, concerns have been expressed about its regulation in South Africa. Some have proposed legislation that governs such issues as transparency on breadth of coverage and representativity, margins of error, modelling of turnout, and any conflicts of interest in polling companies’ relationships with the contestants. 

This is because opinion polls can act as both cause and effect of voter sentiment. The pollsters purport merely to reflect preferences of the electorate. But polls can also inspire or demoralise an election campaign; and their interpretations can be weaponised to sway public opinion.

Most parties consider it a fool’s errand to debate or challenge opinion surveys. However, the parties themselves do rely on their own polling, which helps to refine election strategies and messages. What analysts have not comprehensively done is to assess these opinion surveys post facto, to evaluate whether the pre-election guesses closely approximate the actual outcome. 

Hopefully, debate on these issues will be taken up after the 2026 municipal elections; so we do not wait for the next round of elections before another debate on the rigour, quality and reliability of South Africa’s polling industry.

It is understandable that the data from recent Social Research Foundation (SRF) survey results has generated much debate. Among others, the following figures have been published from the survey, with 2024 figures added for reference:

• ANC support at national level has “declined” to 34% (compared with 45% in 2021 and 40% in 2024) while the DA has improved to 27% (21% in 2021 and 22% in 2024) and the MK party to 15% (14% in 2024);

• In Johannesburg, the ANC polls at 18% compared with 33% in the 2021 elections and 34% in 2024; while the DA is at 42% compared with 26% in 2021 and 24% in 2024; and

• In eThekwini, the MK party polls at 33% (compared with 48% in the 2024 elections), while the IFP surges to 16% (from 5.5% in 2024), and the DA is polled at second place with 23%, compared with 26% in 2021 and 24% in 2024. The ANC dropped from 42% in the 2021 elections to 15% in 2024 and, in the SRF poll, recovered marginally to 18%.

The aim here is not to debate the reliability or otherwise of the SRF survey. This requires accomplished statisticians and psephologists.

It is, however, in SRF’s interpretation of the data that policy preferences shine through, confirming alignment with some of the contestants. Indeed, some of their leaders and staffers – and those of its service provider, Victory Research – have had close associations with the DA. Interestingly, commenting on data about preferences for a new ANC president in future, SRF leader Frans Cronje believes that what would revive ANC fortunes is a leader who abandons the “taxing” of business through black economic empowerment!    

Many commentators compare 2026 polling to 2021 election results. Insufficient attention is paid to the meaning of the 2024 election outcome (compared to 2019), and the new baseline it presents for 2026 and beyond. A rough experiment on where the main parties would have been in the immediate aftermath of the 2024 elections – in relation to municipal contestation – brings this issue of the baseline into sharp relief. The calculation used here is: 2024 results divided by 2019 results and then multiplied by 2021 proportional representation outcomes (2021R X 2024R / 2019R). 

Transposing data across local and national elections requires multiple assumptions; and, of course, much water has flowed under the bridge since 2024. But the exercise presents interesting insights on the starting baseline in 2024 in relation to the coming elections.

So, here goes… 

On aggregate national figures, the ANC in 2024 received 40% of the national vote, from 57% in 2019, with a large number of its supporters – and those of the IFP and the EFF – having migrated to the MK party or towards non-participation. In 2021 the ANC received 46% of the proportional vote. As such, if all things remained equal, the ANC emerged from 2024 with a local government baseline of about 32%. The DA registers just under 22% in all instances, which makes this their baseline; while the EFF’s baseline hovers around 10%. The assumption for the MK party is the 14% they received in 2024.

With regard to the two major metros cited above, a similar exercise suggests the following (using the municipal results from provincial tallies): 

• The eThekwini metro baseline calculation for the ANC is: 14.4% in 2024 from 54% in 2019. Transposing this decline onto the 2021 outcome of 42.5% gives the ANC a 2024 municipal support baseline of about 11%. The DA is stable in the mid-20s; and the MK party received about 48% in eThekwini; and

• In Johannesburg, the baseline calculation for the immediate post-2024 election period takes into account its 32% in 2024 from the 49.6% in 2019. Transposing this decline onto the 2021 ANC tally (33.6%) places its 2024 Johannesburg baseline at about 22%. The DA remains stable in the mid-20s. The MK party and EFF are each at about 12%.

Now, this is a crude experiment, and the data is too dense. There are also too many assumptions; and account has to be taken of ward representation. But the essence of it all is that the ANC emerged from the 2024 election with a low aggregate municipal support base, at about 32%. The DA baseline of 22% was largely unchanged and the MK party’s 2024 baseline is 14%. 

Of course, election outcomes cannot be projected by such crude arithmetic exercises: ceteris paribus (all things being equal) does not apply. And, critically, there have been many ebbs and flows since 2024, profoundly affecting these baselines. 

Whether the parties have significantly shifted their baselines since 2024 and will shift them further depends, among others, on: how each party conducts its campaign; whether it has a convincing vision for local government; whether it is acting decisively to provide services where it governs; whether it fields credible candidates; whether it is as able to enthuse its base to come out on election day; and whether it adequately vets its party agents to prevent any mischief during the tallying. Overlaying all this is the national mood, especially whether voters believe that the country and the economy are going in the right direction.

And so, the salutary lesson for those tidying up the verges and filling the potholes on the road towards the imagined graveside of the ANC or any other party, is: the election marathon is far from the finish line! DM