MEXICO CITY (AP) — What was once Mexico's largest opposition party has approved a policy of running in alliances ahead of next year's presidential election.

Sunday's decision by the leftist Democratic Revolution Party, or PRD, opens up the possibility of ticket-sharing with other unspecified groups that could include the conservative National Action Party. It also extends to gubernatorial races.

The PRD has lost support to the upstart Morena party led by Andres Manuel Lopez Obrador, a two-time presidential candidate who has broken with the PRD and claims to be the only real leftist option.

Such an alliance would be called the Broad Democratic Front. But it could further erode the ideological underpinnings of the PRD, which has moved to the center.

National Action's leader has expressed support for an alliance.