Once again, mass violence has taken the lives of innocents, this time at a nightclub in Orlando, Florida.

As has happened too often these last few years — at the Boston Marathon in 2012, a Colorado movie theater a few months later, a church in Charleston, South Carolina a year ago, an office party in San Bernardino, California last December — blood has been shed and we struggle to understand why. Do we blame radical ideology? Mental illness? Guns? Bigotry? All of the above?

As in Boston, the gunman in Orlando appears to be a homegrown, self-radicalized terrorist. He allegedly swore allegiance to ISIS on the way to the massacre. As in Charleston, this was also a hate crime. Then, the target was African-Americans at a church prayer group. This time, it was gay men at a dance club.

As President Barack Obama said, in a statement of grief and outrage that has become an all-too-familiar ritual during his tenure, “this was an act of terror and an act of hate.”

America should have learned by now not to politicize such tragedies. We should not allow murderers to sway our political decisions, nor should politicians exploit national tragedies for narrow ends.

Those are lessons Donald Trump hasn’t yet learned. Trump’s response to the Orlando massacre was to tweet and brag. He took credit for “being right about radical Islamic terrorism.”

He demanded President Obama resign if he won’t utter the magic words “radical Islam.” He passed on unconfirmed rumors about what had happened inside the nightclub.

Trump’s approach is familiar. The last mass shooting, in San Bernardino last year, prompted his call for a ban on all Muslims entering the U.S. But what might have seemed then a bid to grab attention in a crowded Republican primary field takes on an even darker cast now that Trump has clinched the GOP nomination.

Republicans who have loyally, if reluctantly, pledged their support to their party’s nominee have been hoping for signs that behind the superficial political entertainer hid a mature leader, that the jester could be transformed into a statesman. But Trump continues to demonstrate that he hasn’t a clue about what it means to be presidential. He isn’t even trying.

Hillary Clinton, the presumptive Democratic nominee, took a more measured tone in response to the Orlando massacre. Obama, in his response, showed again what it means to be presidential: He was both resolute and comforting, balancing anger and grief, vowing a thorough investigation and pushing again the kind of common sense gun regulation that could make such crimes less common and less lethal.

Given the partisan polarization of a presidential election year, it’s hard for any leader to ask Americans to come together, even in response to threats, like terrorist violence that endanger people of all political persuasions. But come together we must. In the name of the Orlando victims, and of the hundreds of victims that came before them, we must make our politics worthy of the nation we share and the challenges we face.

— MetroWest Daily News & Milford Daily News in Massachusetts