A major advance for Dilma Rousseff and a major upset for José Serra: this weekend’s Datafolha opinion poll, published in daily newspaper Folha de S. Paulo, shows the leading candidates in Brazil’s presidential election, to take place in October, in a dead heat.

Dilma (as she is known) gained seven points from the previous poll five weeks ago while Serra (as he is known) lost five points, leaving them both with the support of 37 per cent of voters polled. Marina Silva, the former environment minister, was unchanged with 12 per cent. Datafolha says its poll is accurate to within two percentage points.