The Associated Press / Protesters march through Portland, Oregon, last month in what now has been three months of turmoil and violence in the state's largest city.

Democratic presidential candidate Joe Biden could make a number of arguments against the re-election of President Donald Trump in November, but blaming him for violence in American cities this summer — as he did Monday — is not one of them.

Far be it for us to be giving a tip that would bring about the election of such a leftist administration, but that's an issue that won't gain traction from the voters the Democrat needs to win.

Don't like Trump because of his infernal abrasiveness? That's an issue. Don't like the way he has handled the coronavirus pandemic? That's an issue. Don't like the constant turmoil that is the Trump administration? That's an issue.

But the voters Biden needs to win know from whence the violence sprung. It was an outgrowth of the initial peaceful protests that followed the death of suspect George Floyd at the hands of Minneapolis police on May 25.

Although people on both sides of the political spectrum have decried excessive violence by police and sought changes in policies and procedures, it was largely those on the political left who protested. And a subset of those set fires. And looted. And defaced public property. And killed police and innocent people.

For Biden and other Democrats to turn around and assign blame to Trump just doesn't wash. To quote a onetime Hillary Clinton apologist, "There's no there there."

Of course, the former vice president didn't just surface from his basement and pull the issue out of the air. He'd been hearing from advisers and media supporters that he needed to say something about the violence — that the president owned the issue and that Democrats were being hammered on it.

Biden, of course, wasn't going blame those at fault, so — what else? — he blamed Trump.

"He doesn't want to shed light, he wants to generate heat, and he's stoking violence in our cities," the Democratic challenger said in Pittsburgh Monday. "He can't stop the violence because, for years, he's fomented it."

Of course they're just words, but they don't resonate. "Stoking violence?" "Fomented it?"

Americans know the last thing Trump needed during a year in which a virus that originated in China and upended the world was violence. In fact, he's offered to work with states and cities on the use of National Guard troops to help quell the violence, but most have rejected his offer or accepted far fewer troops than he was willing to send them.

Early on, Democrats, if not suggesting in so many words that the violence should continue, thought the unrest would help them. They thought blame automatically would fall to the president if cities continued to burn.

We don't believe they were ever right on that belief. We believe most Americans always saw through it.

That's why Biden assigning blame to Trump is odd.

"That's like the arsonist blaming the firefighter," White House press secretary Kaleigh McEnany said Monday.

But it's part of the "Life in Trump's America" strategy that Democrats hope will resound in a general way. If the confusion from state to state about coronavirus guidelines can be blamed on Trump, if the unemployed in the country because of the coronavirus can be blamed on Trump, if the excessive force misused by police can be blamed on Trump, then the violence from the turmoil that was an outgrowth of the protests of excessive force used by police necessarily must be blamed on Trump.

The Democrats, though, have another problem. Throughout the summer, as violence continued through cities, their mantra — and that of the mainstream media — has been that the violence has been a small aberration, that most of the protests have been peaceful. As recently as Sunday, in an Associated Press news story carried by this newspaper, a daylight scene in Portland depicted tourists happily eating gyros from a food cart and another couple leisurely soaking up the sun. Only later in the story does it say the same city has had 90 straight nights of protests, "frequently ending with vandalism."

So they have two competing stories for voters to swallow — either there's not really much violence or there is violence, but it's all Trump's fault.

Portland Mayor Ted Wheeler, a Democrat, is among those who have put themselves in the middle by not being honest about what is occurring in his city.

"The current national depiction of our city as a dark dystopia with nonstop violence is a lie," he told a cable news outlet.

But in a local interview, Wheeler said, "Nobody can look at those videos [of violence] and say it doesn't raise a whole bunch of questions. There is no circumstance under which that is acceptable or appropriate."

The duplicity by the Portland mayor, among many others on the subject, is in full view. It's hard to hide.

That's why it won't be a winning issue for Biden, either. It strongly suggests a lack of credibility. And he'll need at least a little of that — in addition to destroying Trump's credibility (on which the president too often helps himself) — if he wants a shot in November.