In addition, López Obrador has been vociferous in characterizing the legal proceedings against him as a political campaign, and he has named Fox as a principal figure in the effort.

In a statement read Monday by a presidential spokesman, Fox characterized the land dispute case as "a lack of respect towards the institutions of the nation," and said that a large-scale protest against the action "should not be part of the strategy of one who says that he wants to conduct the nation's destiny."

The statement said that such strategies often serve as a "useful rhetorical tool of authoritarianism" and therefore have no place in a democracy.

"There are still those who believe that the law can be accommodated to fit the needs of those in government," he said. "But no one is correct in showing disrespect for the law."

Defending the case against López Obrador, Fox said that his government is fulfilling a promise to the country to guarantee respect of the nation's institutions. The construction of a "culture of legality implies a certain cost," he said, "and that cost is that people assume responsibility" for their actions.

He also said that the case, known here as the desafuero , is not meant merely to pin guilt and innocence, but is rather "an effort to establish a judicial base by which those who hold an elected office are held accountable."

A legislative committee is currently debating whether to ask Congress to vote on a measure to strip López Obrador of his political immunity. If he were then prosecuted in the case, he would be forced to resign from his current position and forbidden from running for public office in the future.