IHP reveals election-eve MRP Presidential voting intent estimates

IHP’s SLOTS MRP estimates using interviews conducted to 13 September indicate that Anura      Dissanayake would have won the Presidential election on a count of second preference votes  if the Presidential election had been held in early September. 

In the MRP estimates of the views of all adults, Anura Dissayanake led with 48%, followed by Sajith Premadasa on 25%, Ranil Wickremesinghe on 20%, and Namal Rajapaksa on 5%. These estimates were associated with a margin of error of 3–6% for the three leading candidates. The latest IHP MRP modelling indicates that there was a strong surge in favour of Anura Dissanayake since July, when he briefly trailed Sajith Premadasa in voter preferences.

These MRP estimates are based on a substantially revised MRP model (version 4.0) that is still in beta testing. Data came from 20,714 interviews conducted from 31 August 2021 to 13 September 2024, including 541 interviews conducted in September 2024.

IHP Executive Director Dr. Ravi Rannan-Eliya, explained that IHP was forced to substantially                      revise its earlier model, which it had used in previous months. IHP did this to tackle a substantial rise since July 2024 of respondents over-reporting voting for Anura Dissanayake in 2019. This apparent social desirability effect led the previous model to underestimate support for Anura Dissanayake, as the model assumed that only 3% of the electorate cast such a vote. At the same time, this social desirability effect may be associated with respondents telling interviewers that they will vote for Anura Dissanayake when they do not plan to. IHP cautions that these two effects work in opposite directions, and it is not technically possible at the current time to know with certainty which effect is more important. Despite this, IHP has revised its MRP model to assume that many respondents who report voting for Anura                                                                Dissanayake in 2019 did not do so.

With the revised model, IHP estimates that the general trends in voting preference during 2024  were similar to what IHP has previously reported, but that its previous estimates for Anura Dissanayake’s support may have been underestimated by 3–4%.

Dr. Rannan-Eliya commented that in almost all the MRP simulations that were done, Anura Dissanayake had a sufficient lead on the first preference votes to achieve a win once second     preference choices were accounted for. He also noted that in 7% of the simulations, Ranil Wickremesinghe came second overall.

IHP’s SLOTS MRP methodology first estimates the relationship between a wide variety of characteristics about respondents and their opinions  –  In this case, ‘If there was a Presidential  election today, who would you vote for?’ –  in a multilevel statistical model that also smooths month to month changes. It then uses a large data file calibrated to the national population to  predict voting intent in each month since Oct. 2021, based on what the multilevel model indicates about their probability of voting for various parties (‘post-stratification’) at each point in time. The multilevel model was estimated 100 times to reflect underlying uncertainties in the model and to obtain margins of error.

IHP’s data collection covers all districts and communities, and it uses raking to ensure that the estimation samples fairly represent the adult population with respect to age, gender, ethnicity, religion, province and district, sector of residence, relative socioeconomic status, and education.

IHP will release further details of its new estimates in due course. These estimates are released early due to the public interest.