All AtlasIntel polls released after the presidential primaries showed Massa ahead while all other pollsters heavily overestimated Milei’s performance. While most were also pointing to a runoff between Massa and Milei, with the exception of AltasIntel none of them had Massa leading outside of the margin of error.

Most pollsters heavily underestimated Massa even as he was structurally poised to win

• Convergence of left-wing votes: the vote of the left converged for Massa, unlike right-wing votes which were fragmented between Milei, Bullrich, and Schiaretti.
• Turnout mobilization among peronists: the 8pp increase in voter turnout compared to the August primaries (from 70% to 78%) was concentrated among leftwing voters who had failed to turn out in the previous vote due to poor government approval in a context of economic crisis. As such Massa was poised to improve his coalition’s performance beyond the numbers from the PASO. Although turnout was below the historical average, it came slightly above AtlasIntel expectations for Sunday.

Milei’s surprise in PASO generated a chain reaction that was disastrous for Bullrich

While Sergio Massa benefited from uniting the entire leftwing space in the race (Bregman was not a competitive candidate), Bullrich suffered from significant cannibalization with Milei, Schiraretti and even with Massa, as many of Larreta’s voters looked elsewhere following a rough primary within Juntos por el Cambio. Milei’s surprising victory in the primaries anchored him as both the main phenomenon of the race and as the key antagonist to Kirchnerism, but most importantly denied Bullrich the vast majority of the opposition vote within the younger cohorts. AtlasIntel’s estimates for vote migration from Bullrich and Larreta to the other candidates were accurate, being reflected in a very close estimate of her final result.

Even as Bullrich lost some of her voters to Milei, other voters shifted from Milei to Massa and Schiaretti such that overall his result was virtually identical to the one registered in PASO.

Huge volatility among young voters heavily impacted the race

Preferences among young voters proved volatile, with important shifts being witnessed repeatedly during the race. A clear example was Juan Schiaretti’s rise in vote intentions after the 2nd presidential debate, as his passionate characterization of his home province of Córdoba generated a viral reaction on social media platforms.

The huge divide between generations in Argentina is such that if the elections were held only with voters aged 30 and above Bullrich would most likely have reached the second round and won the election. On the other hand, if the elections were held only among young voters (up to 30 years old), Milei would have been elected in the first round with more than 40% of the valid votes. Massa’s lead is explained by his more uniform strength across age groups, even as he was not leading in any cohort.

One of the key dynamics for both campaigns in the runoff will be the pursuit of less politicized voters from the younger generation in a context in which rejection rates for both Massa and Milei are greater than 55%.