Yemeni opposition parties have chosen a politician from the former communist state of South Yemen, Faisal Bin Shamlan, as their candidate.
President Saleh is seeking another term as president
The alliance is made up of the Islamist Islah party, the Yemen Socialist Party, which used to govern the south, and several smaller factions.
This follows the decision of incumbent president, Ali Abdullah Saleh, to reverse a decision to step down.
He is seeking another seven-year term as president.
President Saleh has led the country since the unification of North and South Yemen in 1990. Before that, he was president of North Yemen for 12 years.
Faisal Shamlan held the posts of minister of infrastructure and oil in the socialist government of South Yemen before it merged with the north in 1990.
Since then, he has been a member of parliament in the unified Yemen, and held the post of oil and mineral resources minister.