Over the past 12 years, even with PAN presidents in the National Palace, this broad power structure has remained largely intact. Further, a majority of Mexico’s 31 states have continued to be governed by the PRI machine and its all-too-familiar modus operandi. The only solid opposition stronghold has been Mexico City, which has been relatively well run under three successive PRD mayors.

Without a president to name its candidate, then, for Sunday’s election, the PRI needed a fresh face who was also acceptable to the powers-that-be. Step forward Enrique Peña Nieto, until last year the PRI’s governor in the state of Mexico. At 45, he is too young to be tarred by the PRI’s darkest years. His good looks and actress wife also cast him in a different movie from his Don Corleone forebears. From the shadows, the PRI “dinosaurs” are cheering the makeover.

The main challenger is the PRD’s Andrés Manuel López Obrador, the leftist former Mexico City mayor who claims he was robbed of victory in 2006 and who still terrifies the establishment. The PAN’s candidate, Josefina Vázquez Mota, a former education minister and the first woman to run for the Mexican presidency, was chosen against Mr. Calderón’s wishes but still shares blame for his failures.

All three candidates have sprinkled the land with promises, but at least on the critical issue of drug-related violence, they concur that Mr. Calderón’s “war” is harming Mexico more than the cartels. Their answer is somehow to reduce violence. Fine, but how is this to be done without easing efforts to stop trafficking into the United States? Understandably Washington is nervous.

A more central question is whether a “new” PRI will dare confront the near monopolies — in energy, telecommunications, finance, cement, food and television — that support its return to power and have long profited from the noncompetitive marketplace. Mr. Peña Nieto’s best suggestion so far is to open up the government-owned oil monopoly, Pemex, to some private investment, but that battle lies ahead.

So can the PRI change its spots?

Many Mexicans are deeply skeptical. Already during the campaign, tens of thousands of students demonstrated against a return to the worst of the past.

But in truth I don’t think Mexico would now allow that to happen. A more likely scenario is that, if elected, Mr. Peña Nieto will try to please everyone and will disappoint many. And if he governs only for the PRI’s old pals, he can expect to hear from the Mexican street again.

Alan Riding, a former reporter for The New York Times, is the author of “Distant Neighbors: A Portrait of the Mexicans.”