Amid growing signs that a partial recount won't change enough votes to make him president of Mexico, Andres Manuel Lopez Obrador unveiled a new victory strategy Saturday: he wants the court to throw out results from nearly 5,000 polling places.

"Annulling (the results) from these polling places would change the balance of the election, and would mean that Andres Manuel Lopez Obrador would be the winner," said Claudia Sheinbaum, the leftist candidate's top campaign aide.

She said the request will be filed soon to the Federal Electoral Tribunal, which is overseeing the partial recount and must resolve all challenges to the July 2 elections by month's end.

CountryWatch: Mexico

Parties involved in the recount say elections officials have found extra ballots in some ballot boxes, and in other cases have failed to account for all blank ballots distributed to polling places. Sheinbaum said this suggests "a concerted operation" to distort the vote count in favor of conservative Felipe Calderon, who led by less than 1 percent in the official but still uncertified vote count.

"These criminals thought it was going to be easy, 'we took his victory away and he's going to cross his arms and do nothing," Lopez Obrador said in the Pacific coast city of Tonala in southern Chiapas state. "Well, no, I'm not going to just wait with my arms crossed."

Elections for governor will be held in Chiapas next Sunday and the candidate for Lopez Obrador's Democratic Revolution Party faces a de-facto alliance between Calderon's party and the old ruling party, the PRI, in the governorship race. Chiapas is split by religious, ethnic and political divisions, and is the home to the Zapatista rebel movement, which staged a brief armed uprising in 1994 to demand greater Indian rights.

Representatives of Calderon's conservative National Action Party insisted Friday that no major problems or variations in the vote have surfaced with more than 75 percent of the count completed.

The polling places to be challenged by Lopez Obrador's Democratic Revolution Party were mainly ones where Calderon got more votes, and would represent almost 4 percent of Mexico's voting places, a figure that could rise if more alleged irregularities are found in the partial recount, which is set to conclude Sunday.

Lopez Obrador has said he doesn't want the entire election thrown out, but Sheinbaum said the tribunal might choose to do that, or to order a complete recount of all 41 million votes cast, rather than the current recount of 9 percent of ballot boxes with evident problems.

Some experts have suggested the so-called "missing ballots" might be due to people who kept voting sheets, rather than using them to vote, and said "extra" ballots might have been transferred from nearby polling places. Sheinbaum said neither explanation could account for such widespread problems.

Also, in a Mexican twist on the "hanging chad" dispute that marked the 2000 U.S. elections, the electoral tribunal said it will have judges individually examine questionable ballots that emerge from the partial recount.

Sheinbaum said thousands of ballots could fall into the questionable category.

Mexico has a written voting system in which voters used crayons to make an "x" on a paper ballot in a square corresponding to a candidate, unlike the punch cards that sometimes left incomplete perforations, or "hanging chads," during Florida's 2000 president election recount.

But some ballots apparently have marks that run over more than one square, or no visible marking; such ballots would be reviewed by justices to see whether there was a clear intention in favor of one candidate, or whether they will be considered null or voided.

The tribunal hasn't released any official results from the partial recount, but local media reported that variations of only a few thousand votes have been found, far short of what Lopez Obrador would need to overcome a 244,000 vote deficit.

The protest camps Lopez Obrador followers set up along downtown Mexico City's main boulevard continued in full swing Saturday.