Arguably Senator John McCain’s finest moment came in Minnesota, when he corrected a Minnesota woman who called Barack Obama an Arab, a shockingly widespread belief at the time among Republicans.  With the audience chuckling, and an easy cheap-shot applause line tempting the candidate, McCain showed political discipline, courage and integrity when he famously corrected her. “No ma’am, he’s a decent family man and citizen that I just happen to have disagreements with…”

(By the way, it would have been much more admirable had Senator McCain added something like: “And ‘Arab’ should never be used as a criticism or slur, because most people of Arabic descent are decent family men and women, and many are American citizens who love this country every bit as much as we do.”  That would have been even more courageous and constructive. But I digress.)

Very soon, I suspect Democratic presidential candidates will have their own McCain moment in front of them.  For instance, eye-for-an-eye Democratic activists at rallies will surely echo and mock Trump supporters by chanting “lock him up.”  Though that chant isn’t as racist or removed from reality as the “Arab” remark, it’s also ugly in its own way.

In that same moment, Trump shamelessly promoted ignorance, disinformation, and mob rule by leading the chant, because he is a petty, short-sighted and dishonest authoritarian.  But Democrats should show swing voters that they are better than Trump and his sycophantic Trumpublicans, and should not further normalize Trump’s abhorrent behavior by aping it.

A primary problem with the Trump supporters’ “lock her up” chants was not just that Secretary Clinton hadn’t been found guilty of any jailable offense, or even charged with one.  It also was that politicians should never be making incarceration decisions and declarations about political opponents, Putin-style.  In our American democracy, those are decisions that should be reserved for the independent judicial branch of government, after due process has been completed.

So when the “lock him up” chants inevitably start at Democratic rallies, Democratic candidates and party leaders should immediately stop their crowds and gently but firmly say something like this:

“No my friends, that’s them.  That’s not us.  That’s not how it works in this great democracy of ours. Incarceration is for the judges and juries in the judicial branch to decide, not for us.  But here is something that we can do, and must do. Vote them out!  Vote them out! Vote them out!”

That will show swing voters — Independents, moderate Democrats and moderate Republicans — that Democrats are the adults in the room. It will show them that it’s not true that “both sides do it,” as moderates frequently assert.   It will show them that Democrats are focused on democracy and not being an authoritarian lynch mob.  It show them that Democrats are leaders not demagogues.

For a country suffering extreme Trump fatigue, those things will matter a great deal in the 2020 elections.

Barack Obama showed Democrats the way.  At campaign rallies, his fired up supporters often started  booing their opponents.  But Obama firmly redirected his supporters in a more constructive democratic direction. “Don’t boo. Vote.”

In other words, Obama was a moral leader, not a demagogue.  His wannabe successors will have a similar moral test in front of them in the upcoming campaign.  They need to follow President Obama’s lead.