In a televised speech, Calderon announced that he replaced Fernando Gomez Mont, who angered political allies and upset Mexicans for playing down the deaths of tens of thousands of people in the drug war, with little-known official Jose Francisco Blake.
Calderon, a conservative who took office in December 2006, has staked his presidency on beating back drug cartels fighting over US smuggling routes. But his strategy to send thousands of troops and federal police across Mexico appears to be backfiring. More than 26,000 people have been killed in soaring drug violence over the past 3-1/2 years.
Blake, a senior official in the government of Baja California state, is Calderon's fourth interior minister. He will need to make good on the president's pledge to reform corrupt police and stop drug gangs that extort companies and are scaring off investment in key manufacturing and tourism industries.
"We will do everything we can to meet the public security challenge and the fight against organized crime to recover peace and tranquillity for Mexicans," Blake said at the presidential residence, flanked by Calderon.
As interior minister, the No. 2 position in Mexico's government, Blake will lead negotiations with opposition parties in Congress and oversee national security.
A jump in civilian deaths in Mexico's drug war hurt Calderon in state and local elections earlier this month and deepened Gomez Mont's unpopularity.
Gomez Mont was jeered in a visit to Ciudad Juarez, Mexico's most violent drug war city, after he angered residents by suggesting they should do more to stand up to drug cartels.
"He constantly discredited rights workers, accusing us of working for organized crime. He scolded journalists and lawmakers, he tried to deny what everyone knows, that the violence is part of daily life," said rights worker Gabino Gomez in Ciudad Juarez.
Calderon also wants to regain momentum on reforms to boost its low tax revenue, relax labor laws and allow more foreign investment in the state-controlled oil sector.
Calderon looked nimble on the legislation front early in his term, passing moderate pension, fiscal and energy bills. But since his party lost mid-term elections last year, the president has struggled to push anything substantial through the opposition-led Congress.
Blake will back Calderon's National Action Party, or PAN, that made controversial alliances with left-wing parties in state and gubernatorial elections on July 4, an issue that angered Gomez Mont and helped force his exit.
The PAN paired up with the left-wing Party of the Democratic Revolution, or PRD, it's archrival in the 2006 presidential race, to wrest control of three governor seats from the resurgent Institutional Revolutionary Party, or PRI.
"Gomez Mont's political capital was drastically reduced after July 4, which left him in a very weak position," said Pedro de la Cruz, a political analyst at Mexico's National Autonomous University.
Gomez Mont took his post in 2008 after the death in a plane crash of former Interior Minister Juan Camilo Mourino, who was seen as being groomed to succeed Calderon in the 2012 presidential election.
Calderon also said Economy Minister Gerardo Ruiz was leaving his post and would be replaced by Bruno Ferrari, who had previously headed the government agency that promotes Mexico as an investment destination. Ruiz will now become one of the president's senior advisers.
