If you spend enough time in Democratic politics, you realize we’re less a political party than a large, intense, family Thanksgiving dinner – with a predilection for Robert’s Rules of Order.

Democrats are like the snake cut into eight pieces in Benjamin Franklin's famous 1754 political cartoon, "Join, or Die."

We've got progressives, moderates, democratic socialists, labor Democrats, centrists, institutional Democrats, activists, policy wonks, people who want bold messaging, people who want careful, nuanced messaging – and people who mainly want meetings to end on time.

Disagreement is the norm ‒ Democrats have always argued. Indeed, if we all agreed on everything, I'd suspect someone had accidentally locked us in the wrong meeting or something had been slipped into our food.

Before stumbling into the rumpus of local Democratic politics, I was a history professor. During a career studying and teaching European history, especially the rise of fascism in Germany and Italy in the 1920s and '30s, I quickly learned that democracies rarely collapse because the democratically inclined townsfolk wake up one morning and decide authoritarianism sounds more appealing.

Democracies grow weaker and die when people who broadly agree on democracy become so vexed with one another that they lose sight of the tyrant quietly sawing through the floorboards.

Or to put it more plainly: When democracy is under threat, division among those who believe in it is a generous gift to those who don’t.

Every Democratic faction brings us something valuable

History offers us a powerful warning: Internal arguments become dangerous when we start treating our allies as our enemies, and our genuine enemies as but distant foes over the horizon (or under the floorboards).

In the years before 1933, for example,........

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