Republicans and Democrats don't agree on much, but they agree that sometimes, individual freedom must yield to the imperatives of public safety. They also agree that sometimes, efforts to save lives come at too high a price in liberty. Trouble is, they can't agree on when.
The aftermath of the Las Vegas massacre illustrates how either party employs a different calculus depending on the problem at hand. Each has blind spots that become apparent in moments of crisis.
Consider the GOP pronouncements after the 2015 San Bernardino shootings in which Islamic extremists killed 14 people. Nothing was going to get in the way of a ferocious assault on terrorists.
Chris Christie blamed Barack Obama for failing to grasp "that the most basic responsibility of an administration is to protect the safety and security of the American people." Marco Rubio defended mass electronic surveillance, arguing that after the next attack, "the first thing people are going to want to know is, why didn't we know about it and why didn't we stop it?"
And the Las Vegas massacre? Christie said it "leaves us grasping for answers." Rubio said he was praying for the victims. No one blamed the president. Sen. John Thune, R-S.D., said that people caught in such attacks should, "you know, try to stay safe. As somebody said, get small."
After mass shootings, Democrats demand legislation to ban certain weapons or accessories and restrict access to guns. In these situations, unlike the case with terrorist incidents, Republicans put all their emphasis on personal rights.
Their attitude parallels the Democratic stance on other dangers. Democrats faulted Donald Trump's travel order for stranding a lot of innocent travelers and refugees on the off chance of keeping out terrorists. Some praised Edward Snowden, even though the ranking Democrat on the House Intelligence Committee said his leaks did "substantial damage to national security."
On firearms, the two sides are far apart. Many Democrats have scant regard for the constitutional rights of gun owners. As mayor of Chicago, Democrat Richard Daley insisted on keeping the city's ban on handguns even after the court made clear that it was unconstitutional. Republicans resist any restriction on firearms, no matter how modest.
Gun control supporters are fond of measures that are superficially appealing but practically irrelevant, while opponents treat any restriction as an intolerable violation of liberty.
The Second Amendment, the Supreme Court has ruled, protects an individual right to own guns for self-defense. But no constitutional right is exempt from regulation. I can say whatever I want, but I can't do it on a bullhorn at 3 a.m. I can't drop thousands of leaflets from an airplane.
The court has said that it's fine with a host of existing gun restrictions, such as "laws imposing conditions and qualifications on the commercial sale of arms." If legislators could devise measures that could be effective without imposing onerous burdens, the court might well uphold them.
But many of the ideas heard this week would be irrelevant in practice. To demand a law against so-called assault weapons requires forgetting that the federal ban that existed from 1994 to 2004 had no discernible impact on gun violence.
Washington Post columnist Charles Lane, noting the Las Vegas killer's huge arsenal, tweeted, "What legitimate interest possibly justifies individual possession of 42 repeat 42 firearms?" But only a few weapons are needed to carry out a mass murder. Any numerical limit would be arbitrary and either useless or unconstitutional.
Gun rights advocates, however, reject even the most logical changes if they would cause the slightest inconvenience to any gun owner. The federal government requires licensed firearm dealers to perform a background check for each purchase. But no check is required on private transactions, which account for a large share of sales. When Obama proposed universal background checks in 2013 and again last year, Republicans mobilized to prevent them.
The federal government has no law making a crime of "straw purchasing" -- where a legally qualified person buys a weapon for someone barred from owning guns. When the Senate considered a measure in 2013 to outlaw such commerce, the NRA helped to block it.
What the debate needs is a pitiless focus on options that meet two simple requirements: 1) They hold reasonable promise of being functionally useful, and 2) they don't put an undue burden on law-abiding gun owners.
It's not hard to find measures that meet these conditions. But first, both sides have to want to.