Republican presidential candidate John McCain said Thursday that a shake-up in the leadership of his campaign was part of a "natural evolution" as the organization becomes more national in scope. McCain's campaign announced Wednesday that top adviser Steve Schmidt would assume a broad portfolio of duties, with nearly full control over message and strategy. Schmidt will report to Rick Davis, who will keep the title of campaign manager but focus on longer term matters like the Republican National Convention and McCain's choice of a running mate. Addressing reporters at the conclusion of a three-day visit to Colombia and Mexico, the GOP nominee-in-waiting downplayed the personnel shift. "Our campaign continues to grow, and the responsibilities are expanding and Mr. Schmidt is taking over some increased responsibilities," McCain said. "Rick Davis remains the campaign chairman, campaign manager. It's a natural evolution as we become more and more of a national campaign with increased staff and increased responsibilities." Schmidt disclosed in memo Thursday to the 11 regional campaign managers that he will hire a national political director and a national field director to operate from the campaign's northern Virginia headquarters to improve regional operations and coordination. He said the goal is to increase the capacity to "reach out to voters, build coalitions, identify supporters, and ultimately turn them out to the polls." "In the days ahead, we will be working to enhance and strengthen the coordination between all these aspects of the campaign," Schmidt said. The staff changes - coming after Republican complaints that the Arizona senator's campaign lacked focus and a coherent message - threatened to overshadow McCain's trip through Latin America and his effort to present himself as a statesman experienced in foreign affairs. McCain met Thursday with Mexican President Felipe Calderon to discuss trade and immigration issues. They spoke at length about the Merida Initiative, a US-sponsored effort to stem the flow of drugs and guns across the Mexico border, McCain said. McCain and his wife, Cindy, also toured a federal police station where they reviewed drug interdiction training programs. McCain began the day at the Basilica de Guadalupe, Mexico's holiest Roman Catholic site, where he viewed the famed portrait of the Virgin of Guadalupe and received a blessing from the Basilica's monsignor. McCain laid a wreath of white roses at the altar and stood atop the Papal balcony. He was accompanied by President Bush's brother, former Florida Gov. Jeb Bush, who was in Mexico on business. "I think he's going to win," Jeb Bush said of McCain's chances against Democrat Barack Obama. "He just needs to be himself and not let Sen. Obama redefine himself." McCain's visit to the Basilica had clear political overtones as Catholic and Hispanic voters are expected to be key swing voters in the November election. Obama also has worked to woo Catholics and Hispanics after those groups voted heavily for Democrat Hillary Rodham Clinton during the primary season. McCain's trip to Colombia and Mexico was billed primarily as an opportunity to promote free trade in the Western Hemisphere. Obama has spoken out against NAFTA, the North American Free Trade Agreement, and a pending free-trade pact with Colombia, both of which are unpopular in important general election swing states like Ohio. McCain wants to help workers displaced by free-trade agreements receive job training and other benefits. The McCains were returning to Phoenix late Thursday, and planned to spend the Fourth of July holiday at the family compound outside Sedona, Ariz.