When the opportunity suits him, President Donald Trump has no problem exploiting tragedy for political advantage. Just look at how quickly he reacted after New York police released the identity of Sayfullo Saipov, the Uzbek attacker who mowed down eight people on a bike path in Manhattan on Oct. 31.

Trump promised "extreme vetting" and tweeted: "We are fighting hard for Merit Based immigration, no more Democrat Lottery Systems. We must get MUCH tougher (and smarter)." Saipov immigrated after being randomly chosen in a visa lottery system.

Contrast that reaction, only hours after the attack, to the plodding White House response to the Oct. 1 shooting rampage at the Mandalay Bay hotel in Las Vegas that left 58 people dead and 489 injured. There was no question about the source of the enormous casualty toll: semiautomatic assault rifles modified with "bump stocks" to simulate the rapid-fire ability of military weapons.

But on that issue, Trump insisted that now is not the time to talk politics. It was a time for thoughts and prayers.

After Sunday's attack near San Antonio left 26 dead, the White House repeated the thoughts-and-prayers response. Traveling in South Korea, Trump said that gun control is "a situation that probably shouldn't be discussed right now." Imposing stronger background checks on gun purchasers would have made "no difference" in the outcome near San Antonio, he added.

Gun-rights activists joked that the obvious solution to the Manhattan attack is to ban cars and trucks, or to impose strict background checks on anyone who wants to drive. It's neither funny nor a valid comparison.

Without question, a crazed individual in an automobile can kill lots of people. Semiautomatic weaponry in the hands of crazed individuals can — and do — kill many more, and much more quickly. It is far easier to bring down a rampaging driver than to stop someone armed with hundreds of rounds of ammunition, high-capacity magazines and multiple assault rifles.

Trump was quick to blame Democrats for the so-called Diversity Visa Lottery that put Saipov on an expedited track to enter this country. But he failed to note that Saipov still underwent the same vigorous vetting process as any other visa applicant. Saipov embraced militant Islamism long after taking up residence here.

Trump is impatient with Congress and the judiciary for blocking his proposed restrictions on Muslim immigration. Yet he is the picture of patience as Congress continues to dither on a simple bill to ban the sale of bump stocks.

Trump's supporters want his critics to cut him some slack and take him seriously as our nation's leader. His mercurial approach to crazed mass murderers helps explain why, a year after his election, the nation remains reluctant to get behind him. If Trump wants the nation to follow him, he must lead consistently.

REPRINTED FROM THE ST LOUIS POST DISPTACH