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As newly-inaugurated Mexican President Enrique Peña Nieto settles into office, the country’s new leader is busy filling a number of key staff and high-level government positions.

In what could be the most important appointment when it comes to U.S.-Mexican relations, the Mexican Congress on Wednesday approved Peña Nieto's move to choose Eduardo Medina-Mora as the country’s ambassador to the United States.

Medina-Mora, who will replace the current ambassador in Washington, Arturo Sarukhán, was praised by Mexican lawmakers as having all the characteristics needed to become the country’s representative to its neighbor to the north, according to the Mexican daily El Universal.

Some Washington insiders have also voiced their support for the Medina-Mora appointment, stating that it his previous work with the U.S. on the Mérida Initiative, the U.S. aid program that hopes to restore Mexican government authority in areas challenged by drug traffickers, is a sign that he knows how to work with the U.S. and will have the ear of Peña Nieto.

“It’s likely that the U.S.-Mexico relationship will be run by Medina-Mora out of Washington and straight back to Los Pinos,” said a senior U.S. official, referring to the Mexican president’s residence, according to the Dallas Morning News.

Medina-Mora comes with much more experience than his predecessor and has done a lot in Mexico...His appointment shows that they took the post seriously… they put someone in the position who has directly dealt with the main issue to the U.S., the drug issue.

— Peter Hakim, the president emeritus and senior fellow at the Inter-American Dialogue

Some doubt, however, Medina-Mora’s veracity and worry that the rumors of corruption during his previous position as Mexico’s Attorney General could follow him to Washington.

“While he was the attorney general the PGR (Mexico’s Office of the General Prosecutor) was not seen as a place that invested in integrity or rectitude,” said Adam Isacson, director of the Regional Security Policy Program at the Washington Office on Latin America

Medina-Mora began his career as a lawyer before being appointed Mexico’s Secretary of Public Safety under former President Vicente Fox and then taking over the PGR during the Calderón administration. Since 2009, Medina-Mora has served as Mexico’s ambassador to the United Kingdom, where he dealt with the controversy over derogatory comments made about Mexicans on the BBC show Top Gear.

Upon his arrival in the beltway, Medina-Mora will be faced with two issues that have plagued relations between the neighboring nations for years: Mexico’s drug war and immigration.

Since 2006, when former Mexican President Felipe Calderón declared an offensive on the country’s drug trafficking organizations, an estimated 60,000 people have been killed in the ensuing violence and the war has spread from the U.S.-Mexico border cities to major metropolitan areas like Monterrey and beach resorts like Acapulco.

The war has been a point of contention between the U.S. and Mexico, with the U.S. frustrated over the lack of progress even with the $1.6 billion given to Mexico through the Merida Initiative. The shooting of a U.S. vehicle carrying CIA agents near Mexico City this summer added more fuel to the fire.

Mexico, on the other hand, contends that the U.S. drug habit - which by U.S. law enforcement estimates provides Mexico’s cartels with between $12 to 15 billion per year in cash – and the flow of weapons from the U.S. to Mexico fuels the violence throughout the country.

The botched gun-running operation “Fast & Furious” and the cross-border shooting deaths of some Mexican civilians by U.S. border agents have continued the strain on relations between the countries.

Medina-Mora’s experience as head of the PGR and his service on various posts in the Mexican government puts him in a unique position to deal with the drug issue while ambassador, said Peter Hakim, the president emeritus and senior fellow at the Inter-American Dialogue in Washington.

“Medina-Mora comes with much more experience than his predecessor and has done a lot in Mexico,” Hakim said. “His appointment shows that they took the post seriously… they put someone in the position who has directly dealt with the main issue to the U.S., the drug issue.”

With immigration taking center stage in the national debate throughout the U.S., it will be a key point of discussion between the two countries as Medina-Mora arrives in Washington.

Despite numbers of undocumented immigrants from Mexico dropping during the recession, many migrants from Central and South America still use the country as a conduit to make their way into the U.S. Also, strict immigration laws in states like Arizona, Alabama and Georgia have not only led to anger and alienation from Latinos living in the U.S., but from the Mexican government.

“Mexico cannot conduct effective negotiations with the United States when the foreign policy decisions of the federal governments are undermined by the individual policies of individual states," lawyers for the Mexican government said in a friend-of-the-court brief back in December in reference to Arizona’s controversial SB1070 immigration law.

The lawyers representing Mexico argued Arizona’s ban on harboring of undocumented immigrants harms diplomatic relations between the United States, undermines the U.S.'s ability to speak to a foreign country with one voice and encourages the marginalization of Mexicans and people who appear to be from Latin America.

Despite immigration being a major issue for both nations, some argue that there is little that Mexico’s new ambassador can do to influence the policy in the U.S.

“By and large, the Mexicans realize they don’t get very far trying to push the immigration agenda,” Hakim said. “The best thing is to not get involved in these bitter, partisan issues.”

Along with the appointment of Medina-Mora, Peña Nieto is expected to firm up his foreign policy team by naming security expert and writer Eduardo Guerrero Gutiérrez as his top security advisor.