By Ioan Grillo and Pablo Garibian
MEXICO CITY (Reuters) - In the two days after Enrique Pena Nieto smiled under confetti to celebrate his presidential election win in Mexico, a car bomb killed two policemen, assailants opened fire on a wake near the U.S. border and rival gunmen left 10 dead near the capital.
The carnage served as a grim reminder of the drug war the new leader will inherit when he takes office in December.
Pena Nieto faces pressure from all sides over a drug war that has killed more than 55,000 people in President Felipe Calderon's six-year presidency. The violence undermined support in the government and helped defeat the ruling National Action Party.
The president-elect has to convince Washington he will keep up the fight against trafficking, persuade Mexicans he will reduce the bloodshed and deal with drug-corruption scandals within his own Institutional Revolutionary Party, or PRI.
Pena Nieto has promised to beef up work with U.S. agencies in fighting drug cartels but says he will fine-tune the strategy to reduce violent crime linked to the drug war.
His promised approach will include doubling spending on security, expanding the federal police force to eventually replace the army on the streets and more aggressively chase dirty money.
"I will adjust the strategy so that Mexicans really feel an improvement in security and a reduction in crimes rates, especially homicide, kidnapping and extortion," he said in his first news conference after the election on Sunday.
The switch in focus has sparked some concern that his government won't keep up the arrests of cartel kingpins or could even turn a blind eye on trafficking if gangs tone down their bloodshed in return.
But others argue that Mexico's drug cartels have become so violent, unleashing squads of gunmen with automatic rifles and rocket-propelled grenades, that the government will have to keep battling them whether it wants to or not.
"The drug gangs will ambush Mexican security forces when they are on patrol. They don't have to be provoked," said Mike Vigil, former chief of international operations for the U.S. Drug Enforcement Administration, and a trainer of Mexican marines.
"The drug traffickers feel they are in a war with no quarter asked for and no quarter given, not only with military and police entities, but with rival drug-trafficking organizations. It has evolved into an all-out war of attrition."
Pena Nieto's victory returns power to the PRI, which held the presidency from 1929 until 2000. Its decades of rule was marked by endemic corruption but far less drug-related violence than the country has seen in the past six years.
Tomas Yarrington, the former PRI governor in the violent U.S.-border state of Tamaulipas, has recently been investigated in the United States for ties to drug gangs. Another former PRI governor, Mario Villanueva from the state of Quintana Roo, was convicted on drug trafficking and money laundering charges.
Those cases and evidence of corruption in state and local governments have fueled the claims of critics that parts of the PRI often prefer to work with criminals than fight them.
Pena Nieto has flatly denied suggestions that his government might look to cut a deal with the cartels. "Let it be clear. There will be no pact or treaty with organized crime," he said in his victory speech on Sunday.
To support his predecessor Calderon's offensive against drug cartels, the United States provided about $300 million a year of aid, mainly in training and hardware such as wiretaps and Black Hawk helicopters.
The DEA, FBI and other agencies also became more active here during Calderon's presidency, working with Mexicans to capture top traffickers, such as Arturo Beltran Leyva, who was shot dead by Mexican marines in 2009.
In total, Mexican forces arrested or shot dead 22 of Mexico's 37 top kingpins since Calderon took power in late 2006. But the drugs continued to flow into the United States and the levels of violence soared.
Pena Nieto said he will expand joint efforts to include more stings directed at the cartels' finances on both sides of the border.
"I believe that we can do a lot more together to fight money laundering in particular," Emilio Lozoya, touted as a pick for Pena Nieto's foreign minister, told Reuters.
U.S. officials say publicly they are confident Pena Nieto has expelled the ghosts of the PRI's past and that they have no concerns about the new government's approach to the drug war.
"We are looking forward to continuing the exact same level of cooperation with the Mexican government and enjoying the same level of success that we have had the last years," said Jeffrey Scott, a DEA spokesman in Washington.
NEW POLICE, SAME WAR
At the heart of Pena Nieto's policy is the expansion of the federal police, who currently number 35,000, and the creation of a new "gendarmerie" of some 40,000 officers to keep cartel gunmen at bay in towns and villages.
To help organize these forces, Pena Nieto has brought in the respected former head of Colombia's national police, Oscar Naranjo, as a security adviser.
This move has been welcomed by U.S. officials, who worked closely with Naranjo in attacking Colombian cocaine kingpins.
"Colombia is a success story, cartels are much weaker there. Mexico has to follow this same model to stop turning into a narco state," said Robert Weiner, a former spokesman for a White House's drug control office.
However, Pena Nieto could face a challenge to pass the budget for the expanded security forces through Mexico's Congress, where the PRI and its allies fell short of a majority, according to early vote counts.
Pena Nieto will also face the same fundamental problems of the drug war as Calderon.
In states where troops failed to attack drug gangs, they grew in power. But when troops took out high-profile drug bosses, they were replaced by their lieutenants, who were often even more violent.
"In reality, the room to maneuver to dramatically alter the strategy is very little," said Carlos Ramirez, Latin America analyst for Eurasia Group. "There is no magic bullet."
(Additional reporting by Simon Gardner and Anahi Rama; Editing by Kieran Murray and Philip Barbara)