Zimbabwe's ruling Zanu PF party is expected to file a response in court Monday to the opposition MDC Alliance petition against the election of Emmerson Mnangagwa as president.
Opposition leader Nelson Chamisa said he has evidence to show that he was cheated out of the 30 July presidential vote.
His party says the poll was marred by "mammoth theft and fraud", but the electoral commission insists that there was "no skulduggery".
Mr Mnangagwa won 50.8 per cent of the vote compared with Mr Chamisa's 44.3 per cent.
The judges of the constitutional court have 14 days to rule on the case.