He’s almost certainly going to win. The polls have consistently been showing him leading his challengers by 15 points or more. Polls can sometimes be wrong, but they almost never are wrong at predicting the winner when the gap is this big.
He’s not another Hugo Chávez. Yes, he’s something of a populist and a buffoon, but he’s not a newcomer to politics; he was mayor of Mexico City, and seems to have done at least a passable job at it, and he doesn’t seem to have been a Chávez-style authoritarian while he was in office.
He’s apparently moved to the right in the past year, going by this article in the Washington Post.
The elephant in the living room is corruption. It’s a terrible problem in Mexico, and is intertwined with violence (another terrible problem). While AMLO is atypically clean for a Mexican politician (and this is part of his appeal), it’s unclear whether he’s going to be able to do much about the huge number of corrupt individuals.
Speaking of corruption and violence, his expected victory is mostly the result of Mexicans’ frustration at their country’s domestic problems. It doesn’t have much to do with the Mango Mussolini’s childish insistence that Mexico pay for his stupid wall.