Sex sells, to quote an advertising adage; but fear can be a great motivator too. Witness the surges in gun permit applications after recent mass shootings, including the terrorist attack in San Bernardino, Calif., that left 14 people dead and 21 more wounded.

The National Instant Criminal Background Check System has broken records for firearms background checks every month this year since May, registering more than 2.2 million in November. That doesn't include people buying guns from unlicensed dealers at gun shows and similar venues where checks aren't required.

The Intercept, an online news publication, reports that gun and ammunition retailers like Dick's Sporting Goods have long taken note of the "panic buying" that occurs after mass shootings or perceived threats to gun ownership. An executive for Cabela's, another gun retailer, said it made a "conscious decision" to increase inventory after President Obama's reelection, expecting new customers afraid of more gun control mandates.

It's not just gun dealers, however, who exploit fears to sell a product. Republican presidential candidate Ted Cruz, in his unbridled attempts to corral the conservative wing of his party, seems to be banking on fear to help him do so. "You don't stop bad guys by taking away our guns; you stop bad guys by using our guns," he declared at an Iowa shooting range recently.

The Texas senator unveiled a new TV ad that criticizes the Obama administration's inability to defeat Islamic State, which apparently inspired the San Bernardino attack but did not direct it. "If I'm elected to serve as commander in chief, we won't cower in the face of evil," Cruz says in the ad. "We'll kill the terrorists. And every Islamic extremist will know, if you wage jihad against us, you're signing your death warrant."

Cruz may talk like a character from a John Wayne movie, but he has moved up in Iowa's polls, which reflect his appeal to gun-rights voters and evangelical Christians. Taking notice is Florida Sen. Marco Rubio, whose campaign for the Republican nomination has begun targeting Cruz to gain right-wing support. In most polls, both Cruz and Rubio trail Donald Trump, who said of the victims of the San Bernardino shootings, "They could've protected themselves if they had guns."

That sentiment is evident in the number of Americans who want guns. Have they forgotten that there was a time when it was common to walk around parts of this country with a sidearm and be ready to draw it? They called it the Wild West back then because life there was precarious; whoever had the biggest or most guns called the shots.

Perhaps the Supreme Court thought of that this month when it departed from previous pro-gun rulings and refused to void a Chicago suburb's ordinance banning assault weapons and high-capacity magazines. There must be reasonable limits on gun ownership to battle gun violence.