Datafolha puts Lula four points ahead of Flavio Bolsonaro, and the runoff inside the margin

President Luiz Inacio Lula da Silva leads Senator Flavio Bolsonaro by four points in the first round of Brazil's presidential election, and the two are inside the margin of error in a runoff, a Datafolha poll released on Thursday shows. Voting is this weekend.

Datafolha put Lula, of the Workers' Party, at 42 percent of first-round voting intentions and Flavio Bolsonaro, of the Liberal Party, at 38 percent. In a second-round matchup the same survey has Lula at 48 and Flavio at 45. The margin of error is two percentage points either way. A four-point first-round gap is outside that band. A three-point runoff gap is not. The institute interviewed 2,506 voters between Tuesday 29 September and Thursday 1 October.

The four-point gap is unchanged from the previous Datafolha, taken a week earlier. On 24 September Lula had 40 and Flavio 36. The runoff that week was 47 to 45, also a technical tie, with the president numerically ahead. Both men have gained two points. Neither has gained on the other.

The rest of the field is small. Augusto Cury of Avante has 4 percent. Ronaldo Caiado of the Social Democratic Party and Renan Santos of the Mission Party have 3 percent each. The race Datafolha is measuring is a two-candidate race with a scattering of others who, on these numbers, do not reach the second round. Brazil's system sends the top two to a runoff if nobody wins a majority of valid votes on Sunday.

Flavio Bolsonaro is the eldest son of former president Jair Bolsonaro, who is not on the ballot. The comparison that matters for readers of the last election is the 2022 first round, when Lula took 48.43 percent of valid votes and Jair Bolsonaro 43.20 percent. Lula won that runoff. The 2026 first-round poll, at 42 to 38, is a tighter opening spread than the 2022 result, and it is a poll rather than a count. Datafolha's own note on the earlier cycle is that the actual 2022 result was closer than some of the pre-election surveys. A four-point lead with a two-point margin is not a forecast of Sunday's tally.

The runoff figure is the one campaigns will argue over if Sunday produces no majority, which the first-round numbers suggest it will not. A candidate at 42 percent needs the votes of the 4 percent with Cury, the 3 percent with Caiado, the 3 percent with Renan, and the blank and undecided, or he needs the other side's voters to stay home. The poll does not publish a full transfer table. It does publish the head-to-head, 48 to 45, which says that when respondents are forced to choose, the gap shrinks from four points to three and falls inside the error band.

A technical tie is a statement about the sample, not a statement that the candidates are equal. With 2,506 interviews and a two-point margin, a three-point runoff lead can appear by chance. A four-point first-round lead is less likely to be chance, and it can still vanish between Thursday and Sunday. The previous week's poll showed the same shape at a lower level, 40 to 36 and 47 to 45. The shape has been stable for seven days. Stable in a poll is not stable in a count.

The rejection numbers in an earlier Datafolha, taken on 1 and 2 September with 2,002 voters, had 47 percent saying they would not vote for Flavio and 45 percent saying they would not vote for Lula. That survey is a month old and a different sample. It is the closest published measure of the ceiling each man faces. A candidate rejected by nearly half the electorate can still win. He cannot win by addition alone. He wins by the other man being rejected too.

Sunday is the first round. If the Datafolha shape holds, the country will know on Sunday night that there is a second Sunday, and it will not know from this poll which name is ahead in it. The useful figure from Thursday is the pair: 42 to 38 now, 48 to 45 if it goes on, both men up two points in a week, the gap unchanged.