calderón's campaign gained momentum after the first presidential debate. subsequent poll numbers put him ahead of lópez obrador from march to may; some polls favored him by as much as 9 percentage points. this trend in his favor was contained after the second presidential debate when lópez obrador decided to start joining the debates. final poll numbers days ahead of the results indicated that his opponent's prior lead had shrunk further; some polls gave lópez obrador the lead, while others favored calderón and still others indicated a technical tie.