Mexico leftists yet to declare new party leader

MEXICO CITY, March 23 (Reuters) - Mexico's leftist opposition party was still without a new head on Sunday as party officials disputed ballots from last week's leadership election and claimed irregularities with the vote.

Alejandro Encinas, who could steer Mexico's No. 2 political party on a more radical path, declared victory last week with a small lead in preliminary results. But vote counting since then points to a stronger finish for moderate Jesus Ortega.

The election will decide whether the left, whose 2006 presidential candidate Andres Manuel Lopez Obrador says his defeat was rigged, settles in to a combative stance or becomes a more conciliatory political force as the government tries to push an oil sector reform through Congress.

Supporters of both candidates to lead the Party of the Democratic Revolution, or PRD, accuse the other of intimidating voters, stealing ballots and interfering with counting. Several polling stations have yet to turn in their final tallies, local media reported.

The party had set a Sunday deadline to finish vote-counting but a few closely disputed regions were not expected to be completed.

PRD founder Cuauhtemoc Cardenas said in an open letter Saturday that systematic rule-breaking and lack of ethical principles meant the vote should be annulled. But Ortega and Encinas both dismissed Cardenas' call.

An Encinas win would increase the chances of a political comeback by his mentor, firebrand Lopez Obrador, who has seized on the oil debate to hold street protests against the idea of allowing private partnerships in the state-run sector.

As party leader, Encinas would likely bolster the protests, which could extend to road and airport blockades, and raise the chances of Lopez Obrador having another shot at the presidency in 2012.

Encinas could also pull PRD lawmakers out of a congressional debate on the planned energy law, President Felipe Calderon's most ambitious reform attempt yet, experts say, whereas Ortega has vowed to fully participate in talks. (Reporting by Noel Randewich)