An African American is killed by police. Protests follow. Some turn violent. It's been a recurring story of 2020. But as much as the vast numbers on the streets reflect a movement for greater equality and for change, the backlash to the demonstrations also galvanised support for President Donald Trump, revealing one of the great dividing lines of this election. Just days before polling day, another tragedy followed by nights of unrest reminds us of one of the central issues of the US election, one which many say is driving their vote. But what exactly that issue is depends upon which side of the great American divide the voter finds themselves. For some, the fatal shooting by police of Walter Wallace in Philadelphia is yet more evidence that sweeping change is needed to tackle the twin scourges of police brutality and systemic racism. Mr Wallace was a 27-year-old black man who was carrying a knife and had, it appears, been suffering a mental health crisis. His family say they had called the emergency services themselves, but for medical help. "Our hearts are broken for the family of Walter Wallace Jr, and for all those suffering the emotional weight of learning about another black life in America lost," began a statement from Joe Biden. For some Americans though, it is the civil unrest in the aftermath of the killing that is their focus. President Trump speaks to those voters with his strong law and order messaging, talking of the rioting and looting. "You can't let that go on. Again, a Democrat-run state, a Democrat-run city, Philadelphia." President Trump is once again facing accusations, in what is a key battleground state, that he is stoking unfounded fears of chaos and lawlessness under a prospective Biden administration. But there are those who feel strongly that the president is right and just in the past few months we have met them in cities around the country. Take Holly Tuttle-Bathuly, who was among those turning out on in early September - amidst the "Thank you" placards and American flags - to greet Mr Trump when he visited Kenosha, in another crucial electoral state, Wisconsin. "He is the only one who helps us, who else can help us?" she said. "I just want to encourage him to continue to have our backs." The president was visiting the week after Jacob Blake, a 29-year-old African-American, was shot seven times in the back and paralysed by an officer.