President Vicente Fox fired his attorney general last night to try to end a crisis over legal charges that threatens to knock Mexico's most popular politician out of next year's presidential elections.
Under intense pressure, Mr Fox fired Rafael Macedo, the attorney general who led the campaign to put Mexico City's leftist mayor, Andres Manuel Lopez, on trial for contempt of court charges in a land dispute.
The move was a victory for Lopez Obrador, who holds a strong lead in polls for the elections but would be blocked from running if found guilty in the case.
Mr Lopez Obrador accused Mr Fox's conservative government of pushing bogus legal charges to block his road to the presidential palace.
"My government will prevent no one from participating in the next federal election race," Mr Fox said in a national television and radio address.
He said his new attorney general would thoroughly review the case against Mr Lopez Obrador and "look to preserve the greatest political harmony within the limits of the law".
Hundreds of thousands of Mexicans marched in silence through the capital last Sunday in support of Lopez Obrador, a former Indian rights activist who promises to work for Mexico's poor if elected.
Mexican stocks have dropped more than 10 per cent since March 7th and an easing of the crisis is likely to be welcomed by financial markets.