For the 840,000 members of Latin America's biggest leftwing party, these are stressful times. Just under three years after its leader Luiz Inácio Lula da Silva became president of Brazil, the Workers' party (PT) has been enveloped by accusations of corruption.

Tomorrow's internal elections, when party members vote for a president and executive committee, will highlight deep divisions in an organisation whose unity has been one of the most predictable features in Brazil's political landscape.