The largest trade union in South Africa says it will no longer support the African National Congress - a big blow for the governing party.
The National Union of Metalworkers of South Africa, which has 330,000 members, said it would not endorse any party.
Trade unions and the Communist Party have been in a alliance with the ANC since 1994.
But poor South Africans have become increasingly critical of the ANC, which they accuse of corruption and not doing enough to tackle poverty.
Like other unions, NUMSA members went on strike earlier this year to demand higher wages.
Last week, President Jacob Zuma was publicly booed at the memorial service for Nelson Mandela.
NUMSA head Irwin Jim on Friday called for Mr Zuma to resign, saying his administration has been linked to too many scandals.
He said the union would explore the possibility of setting up a new, socialist party.
But a BBC correspondent said NUMSA did not completely cut its ties with the Congress of South African Trade Unions, which remains in alliance with the ANC.