On Saturday, Welshman Ncube, who led a break-away MDC faction in 2004 and Tendai Biti, who left the main opposition in 2014, signed a pact that would see them fielding parliamentary candidates in some constituencies under the MDC Alliance banner and would support Tsvangirai’s fourth bid for the presidency.
Mugabe, 93, has ruled the former British colony since independence in 1980.
Ncube and Biti are founding MDC members who both held the position of secretary general and served as cabinet ministers in a unity government with Mugabe’s ZANU-PF until a crushing defeat in the 2013 election.
Two other smaller political parties led by a former army general and Mugabe ally Agrippa Mutambara and Jacob Ngarivhume are part of the election alliance that was signed in Highfield township in the capital Harare.
“We are saying today, this convergence is not just about political parties. It is to stop fragmentation. Mugabe has no excuse to rig if we are united,” Tsvangirai told supporters after the signing ceremony.
Biti added: “We owe it to the thousands of Zimbabweans to make sure that in our lifetime we can remove the beast called ZANU-PF.”
The opposition accuse Mugabe of rigging his way to victory in previous elections and say he has used political violence and the state security apparatus to maintain his hold on power. Mugabe denies the claims.