Part of this is due to the fact that while Mexicans are generally displeased by Calderon's results, polls suggest they are in surprising agreement with the basic outline of his strategy. Only a small minority of the public wants to see a pact with the criminals at one extreme or an even more violent military campaign at the other. So the candidates end up dancing around the issue, offering modest alterations to Calderon's framework.Good question.
What will be interesting is whether in the final months of the campaign as one candidate is down in the polls if he or she throws that Hail Mary pass and offers something completely different to try to distinguish their policies and draw media attention and votes.
I also feel compelled to add that no sooner was that piece published than half the slate of candidates began to prove me wrong. Here's AMLO and Creel returning to the familiar terrain of Calderón-knocking, and here's Vázquez Mota proposing life in prison for dirty politicians. More on that second part in a bit.