New York Mayor Michael Bloomberg has, by all accounts, put serious thought into seeking the presidency.

There was a good deal of spectulation heading into the 2012 contest—as there had been heading into the 2008 contest—that the billionaire businessman (the eleventh-wealthiest American) who once seemed to be the last hope for liberal “Rockefeller Republicanism” before switching his party affiliation to “independent” during the latter stages of the Bush-Cheney interregnum, might run on a new third-party line or as an unaffiliated contender. But it never happened.

So Bloomberg is campaigning without the campaign.

Since last month’s Dark Knight shootings in Aurora, Colorado, last month, the mayor of the nation’s largest city has emerged as the most outspoken advocate for an active and engaged government response to a rash of gun violence. And now, following the horrific shootings at the Sikh Temple of Wisconsin—in which an alleged white-supremacist gunman killed six worshipers and shot many others, including a police officer—Bloomberg has coupled his antiviolence advocacy with a renewed championship of religious tolerance.

Appearing with Sikh leaders at a community center in the New York borough of Queens, Bloomberg declared, “No matter who you are, no matter where you’re from, no matter what religion you profess, you have a right to be safe in your homes, in your places of worship and in the streets of New York City. We have no tolerance for intolerance.”

That was a more aggressive line than the ones taken by President Obama and his Republican challenger, Mitt Romney. Both Obama and Romney made sound and sensitive, if rather tepid, statements. Romney decried to the killings as “a senseless act of violence and a tragedy that should never befall any house of worship.” The president, who ordered that US flags be flown at half staff at the White House and other officials buildings through Friday, offered a soft embrace of the religious tolerance: “It is important to reaffirm that regardless of what we look like or where we come from or where we worship, we are all one people and we look after one another in this country,”

Asked whether the killings in Oak Creek, Wisconsin, like the killings in Aurora, Colorado, might call for a revisiting of the gun-control debate, Obama went vague: “All of us are heartbroken by what’s happened. I think all of us recognize that these kinds of terrible, tragic events are happening with too much regularity for us not to do some soul-searching and to examine additional ways that we can reduce violence.”

Compare that to Bloomberg.

“Just two weeks after the tragedy in Aurora, Colorado, we’ve seen another mass shooting,” the mayor declared on the steps of a Sikh center in Queens. “One in which it appears there were some warning signs in the shooter. And still the two presidential candidates have not given the American public a plan to keep guns out of the hands of dangerous people. Every day thirty-four Americans are murdered with guns. The fact that criminals, terrorists and other mentally ill people have access to guns is a national crisis.”

And Bloomberg leaves no doubt that the presidential contenders of both major parties are failing to address that crisis.

Noting that Romney once backed sensible gun-control laws but now staunchly opposes them, Bloomberg said, “The governor has, apparently, changed his views, and the president has spent the last three years trying to avoid the issue, or if he’s facing it, I don’t know anybody that’s seen him face it. And it’s time for both of them to be held accountable.… Leadership is leading from the front, not doing a survey, finding out what the people want and then doing it. What do they stand for, and why aren’t they standing up?”

In the face of what he dismisses as “deafening silence” from Obama and Romney, Bloomberg is blunt, outspoken and headline-worthy.

He is not a candidate.

But he is campaigning.

Where does that take Bloomberg ultimately? Not into the 2012 race as a contender. It is far too late for that; filing deadines have passed and the presidential race seems to have settled into a pattern that will continue through November.

So does Bloomberg really thinks he might be able to run for president in 2016, at the age of 74?

That’s politically adventurous. But Bloomberg has pushed limits before, as a Republican in New York, a party-switcher and a famously—if, arguably because of his New York perch, safely—outspoken politician. His politics are those of an old-school Republican moderate, so it would be silly to imagine him as a transformational politician. But he is staking out high ground when it comes to combatting gun violence and defending diversity.

Bloomberg is asking the right questions about why those who would assume the presidency are so deafeningly silent. And it should come as no surprise that, in this era of increasingly content-free political discourse, the mayor’s voice is going to continue to resonate.