The Institutional Revolutionary Party (PRI), Mexico’s third political force, notched up an important local-election result on Sunday in a sign that the party is on its way to performing strongly in next year’s vital mid-term congressional elections.

By Monday afternoon, and with almost all the votes counted from Sunday’s poll in the southern state of Guerrero, the PRI had won 13 of the 28 directly elected seats in the state legislature from nine three years ago. It also won 40 of Sunday’s 81 mayoral elections.