After delivering a short campaign speech in the central plaza of Dolores Hidalgo (pop. 85,000), Cuauthemoc Cardenas walked to the museum honoring the local priest who in 1810 issued the call to arms that sparked Mexico's wars of independence. Adjusting his glasses and removing a pen from the pocket of his tailored white shirt, the left's candidate in next week's presidential elections hovered over the visitors' book. "I pay homage to Don Miguel Hidalgo," he wrote. "His sacrifice inspires us to take up once again the struggle for our independence and freedom."
Those words, to which Cardenas appended a signature every...