Thousands marched through Mexico City, railing against what they called the “imposition” of the old ruling party candidate as the country’s new president.

Leftist activists blockaded bank headquarters and called for a march on the offices of federal prosecutors, as officials recounted some of the ballots from Mexico’s disputed presidential election.

Mexico’s main leftist candidate plans to challenge the presidential vote tally at tens of thousands of polling places, and also will allege that attack ads by the apparently victorious conservative were illegally harsh, a top adviser said today.

Mexico’s ruling party’s Felipe Calderon had an insurmountable lead in today’s presidential vote count, but his leftist rival vowed to challenge the results in court, setting the stage for a long battle over who will lead the nation’s young democracy.

FELIPE Calderon became president-elect of Mexico yesterday, two months after disputed elections, when the nation’s top electoral court voted unanimously to reject allegations of fraud and certify his narrow victory.