On 15 occasions during his presidency, Barack Obama has had to speak at White House press conferences about mass shootings. During that time, his response has changed. Where once there was a determination to strengthen American gun safety laws, there is now utter frustration. His failure in that area, he said recently, had caused him more distress than anything else.
This week, therefore, the President would have been heartened by the vow of Democratic presidential frontrunner Hillary Clinton to tackle gun violence. Days after another mass killing, this time at an Oregon community college, she unveiled an ambitious new set of controls on the selling of firearms.
The rest of a bemused world nodded its agreement. Many Americans, however, were far from convinced. If she is elected, Mrs Clinton will face no easier a task than Mr Obama. First, there is the shameful opposition to reform by the Republican Party, which controls Congress. Ms Clinton says executive action would be used to clear that hurdle.
But, most fundamentally, she will have to change the mindset of many Americans. They value freedom and liberty, as enshrined in the US Constitution, above all else, and refer repeatedly to its Second Amendment.
This dates from a time when militias were maintained, and has no relevance today. But it continues to be interpreted as granting all Americans the right to bear arms. And as common as mass shootings have become, many, astoundingly, still see no reason to surrender that right.