Three mayors have been assassinated in Mexico since the New Year, with hardly a blip on the media screen here.

Contrast that with the nationwide mourning that took place in the United States after the Arizona shooting left six dead and a lawmaker critically injured and some wonder whether Mexico has lost its ability to be shocked.

Unlike the shooting that targeted US Congresswoman Gabrielle Giffords (D) from Arizona, the mayoral assassinations did not dominate national headlines in Mexico. The victims were not memorialized by the president, and candlelight vigils were not held at state capitals in their honor. For most people, their deaths passed unnoticed as police blotter.

IN PICTURES: Mexico's drug war

“I can’t help but notice the difference in the response to the attack on the congresswoman in Arizona – which brought the US government to a standstill – and the lack of [government] response in Mexico when a journalist, mayor, or civic leader is killed,” says Andrew Selee, director of the Mexico Institute at the Woodrow Wilson Center in Washington. “Killing them is not only silencing an individual, but is silencing society.”

On pace to see 72 mayors killed this year

The Mexican mayors murdered were Luis Jimenez Mata of Santiago Amoltepec, Oaxaca; Abraham Ortiz of Temoac, Morelos; and Saul Vara Rivera of Zaragoza, Coahuila.

Three assassinations in two weeks represents a stark rise in mayoral killings from 2010, when as many as 14 mayors were murdered in the entire year, most of them by suspected criminal organizations. The killings come as the four-year death toll from the drug war recently hit 34,612, with a record-high 15,273 deaths alone in 2010.

BACKGROUND BRIEFING: Mexico drug war death toll up 60 percent in 2010. Why?

The beheading of 15 people in Acapulco last week underscored that horrific acts will likely continue as the drug war drags on. And yet, on occasion, people do fight the complacency that has grown with the death toll.

Lack of sympathy for politicians

On Thursday a broad coalition of human rights groups wrote to President Felipe Calderón after another egregious act received little response from the president: the murder of a second activist who fought against women homicides in Ciudad Juárez.

Susana Chavez of the group “Not One More Death” was found dead with her hand severed on Wednesday. And last month Marisela Escobedo Ortiz was shot in the head outside the governor’s palace in Chihuahua City near Juárez after she demanded that the killer of her teen daughter face sentencing. Her death sparked a nationwide outcry.

The mayors may have received less public attention than the activists, and far less play than Congresswoman Giffords in the US, because of a common belief that many in the political class get into trouble for moonlighting with drug cartels.

“There is no clean politician,” says Francisco Carral, a Mexico City refrigerator engineer. “If there were, this wouldn’t happen to them.”

Calling on Calderón

But mayors are often threatened if they don’t comply with traffickers, or are killed for refusing to follow the orders of criminal groups, security analysts say. Their deaths in larger numbers will only increase a climate of ungovernability in parts of Mexico, the analysts warn.

In the US after the Arizona shooting, "the nation stood still, held a moment of silence. In Mexico, all they say is ’Who's next?’ ” tweeted Sergio in Spanish on Monday from Brownsville, Texas, which borders Mexico.

“We are all about the numbers, but we’ve lost the dimension of their [identities],” commentator Sabino Bastidas said on the local W Radio show Friday, highlighting the stark difference between reaction in Mexico to political killings to President Obama’s speech Wednesday in Tucson that mentioned each of the Arizona victims by name.

President Calderón has flown into cities on occasion to speak with victims’ families, and introduced a social program in Juárez last year after 15 teens were killed at a birthday party. If the president would send his top officials each time to investigate the worst of the murders, like Mr. Obama did in Arizona, it may have drug groups thinking twice before targeting politicians and activists or massacring civilians, says Mr. Selee of the Woodrow Wilson Center.

“What cartels fear the most is that the government will get in the way of their business. So the response needs to be…get in the way of their business,” Selee says.

IN PICTURES: Mexico's drug war