In response to Obama's dramatic moves in the U.S. war on drugs -- and his forceful acknowledgment that Americans share the blame for violence south of the border -- Mexico has agreed to set aside questions of sovereignty and pride, and accept U.S. help in unprecedented ways.
The new tone has made it easier for President Felipe Calderon to welcome increased U.S. border security and even U.S. training for Mexico's navy. Prosecutors from both countries now plan to evaluate drug cases together and put captured traffickers on trial in whichever country promises a tougher sentence.
"The message finally seems to have gotten through -- beyond the rhetoric -- that the U.S. needs to do more to fight drug trafficking and arms trafficking, and that actually is translating into policies," said Maureen Meyer of the Washington Office on Latin America, a nonprofit organization promoting social and economic justice in the region.
Obama has moved quickly to provide more money, technology and manpower to secure the U.S. border region, including committing 500 more federal agents to stem the flow of illegal weapons into Mexico and seeking $350 million in new Pentagon funds to help Mexico fight drug trafficking. Congress already has approved $700 million for training and equipment in Mexico to battle the cartels.
Obama also ordered the Justice Department to go after the smugglers of guns and money who fuel Mexico's violent cartels, which have penetrated deep inside the United States.
Still, when Obama and Calderon sit down together on Thursday, they each must overcome long-standing cynicism about how the drug war is being fought on the other side of the fence.
Mexico is demanding more politically difficult moves by the U.S. government -- namely, reinstating a 2004 assault weapons ban. It also wants the U.S. to do more to confiscate drug money before it reaches Mexico, reduce consumer demand for illegal drugs, focus intelligence on gangs that move drugs in the U.S., and do more to seize marijuana, which accounts for half the estimated $10 billion cartels make in U.S. profits each year.
Top U.S. concerns include corruption and the slow pace of judicial reform in Mexico. Despite some high-profile arrests of police officials, cartels still easily buy off Mexican law enforcement, and most crimes go unpunished.
"It's a good time for the two countries to combat their shared problems because they have realized they need each other," said Victor Clark, a Tijuana-based border expert who teaches at San Diego State University.
More details could emerge after Obama and Calderon meet. Obama then leaves for the Summit of the Americas in Trinidad on Friday morning.
The U.S. and Mexican governments have always professed close relations -- Presidents Vicente Fox and George W. Bush rode horses on Fox's ranch and vowed immigration reform -- but much of the rhetoric proved empty after the 2001 terror attacks diverted Washington's attention.
Obama and Calderon have been careful not to spend their political capital on immigration reform at a time of economic crisis, and have found a shared purpose in battling the drug war.
More than 10,650 people have been killed in drug violence in Mexico since Calderon sent out 45,000 troops in 2006 to directly confront the traffickers. Calderon's refusal to back down despite the bloody toll has gained him praise and credibility, as have a series of high-profile arrests, nabbing four of Mexico's 37 most-wanted traffickers in just the last few weeks.
The Mexican government points to another sign of progress: drug killings are down 26 percent this year compared to 2008.
And while human rights groups want Obama to push Mexico to do more to address escalating complaints of abuses by its military, Obama has tried to smooth tensions instead -- denying, for example, that Mexico is on the verge of becoming a failed state, despite a U.S. military report that warned Mexico is at risk of "rapid and sudden collapse."
The overtures have made it easier for Calderon to accept U.S. help that would have been politically unfeasible just a short time ago.
The Mexican Congress on Tuesday was debating Calderon's request to allow the navy to do counter-narcotics training in Florida with the U.S. Coast Guard. Such military exercises have been blocked by distrust that dates to 1848, when the U.S. took half of Mexico's territory in the Mexican-American War. Unlike Colombia, Mexico does not allow direct U.S. military involvement, and Calderon says that won't change.
Mexico's Congress also is debating legalization of marijuana, a political long shot that is gaining currency. Calderon has proposed offering treatment instead of jail time, but would not legalize possession.
The economic crisis also is on the table, and both leaders hope to resolve disputes such as Washington's canceling of a program that gave Mexican truckers access to U.S. highways, which prompted Mexico to retaliate with tariffs on about 89 U.S. products representing $2.4 billion in annual trade.