It has come down to this.

A U.S. senator calls the president “Cadet Bone Spurs.” The president says Democrats who sit on their hands during a speech are “treasonous.” The president also uses Twitter to blast out insults daily, hanging nicknames on his political foes here at home — and abroad.

According to an analysis on CNN.com, Donald Trump has managed to bring other political leaders down to his level. He has made insults the game of choice among political leaders.

Sen. Tammy Duckworth, an Illinois Democrat, was moved to hang the Cadet Bone Spurs epithet on Trump after the president accused Democrats of being “anti-military.” Duckworth, a former U.S. Army helicopter pilot who lost both legs when her chopper was shot down during the Iraq War, was personally insulted that this president would say such a thing about his fellow Americans. Hence, the reference to Trump’s medical deferments during the Vietnam War.

These childish insults denigrate the political discussion. They drag the quality of everyone’s argument into the gutter.

It boils down, in my view, to the source of this denigration.

To me, it’s clear: Donald Trump started this downward journey with his Twitter-based insults launched during the 2016 presidential campaign. He promised to curb that activity once he got elected. Has he delivered on that pledge? Nope. It’s gotten worse.

As the analysis provided on CNN.com points out, the president has dragged others down this disgraceful path with him. One of the followers appears to be chief of staff John Kelly, who this week said the so-called immigration “Dreamers” need to “get off their asses” if they want a path to citizenship.

Oh, my.

This is how you “unify” the nation? I don’t believe so.