SAN FELIPE, Venezuela — Nicolás Maduro is certainly not the first political candidate to invoke the name and legacy of a dead leader to win votes. But he may be the first to say that his political mentor, President Hugo Chávez, visited him from beyond the grave in the form of a little bird. In what stands out as the most surreal moment of Venezuela’s presidential campaign — a race whose central personality is the deceased president — Mr. Maduro told the nation that Mr. Chávez’s spirit came to him as a tiny bird that flew into a chapel where he was praying. So now at campaign rallies he whistles like a bird.