Between 1790 and 1970, the first 180 years of American history under the Constitution, 36 presidents served this nation. Only one of those three dozen presidencies produced an impeachment crisis.

That was when Andrew Johnson, an ill-tempered, anti-secession Southerner and accidental, unelected president, was impeached by the House but kept in office by one vote in a Senate trial, all amid a poisonous storm of bitterness that followed America's blood-drenched Civil War and Abraham Lincoln's assassination.

In the 50 years of U.S. history since 1970, three of nine presidencies have now been overtaken by a formal impeachment battle.

One could be forgiven for spotting a noteworthy change here in American political norms. A 12-fold increase in the prevalence of presidential impeachment within the lifetimes of today's senior citizens, compared with all previous American history, looks suspiciously like a new trend, and maybe not a healthy one for democracy.

Our historically challenged era should ponder a longer view of events every now and then. Democrats' decision to embark on an impeachment inquiry against President Donald Trump may not be all about Trump and his singular misbehavior and misdeeds (though it's partly about that).

It also may not be all about the so-called Great Awokening and its angry radicalization of American progressives (though it's partly about that, too).

President Andrew Johnson.

The new normalization of impeachment may have as much or more to do with deep structural deformations in our political and social systems for which the living generation of Americans bears much (not all) responsibility — and whose consequences could extend far beyond the current clown show.

The impeachment of a president — any president — is more than the attempted ouster of an unworthy politician from a powerful office. It is the attempted overturning of the result of a national election. Through impeachment a decision made by many millions of voters is repudiated, not by fellow voters but by rival politicians, mainly sworn enemies of the target. The Constitution permits this because there must be some ultimate check on outlawry in high places.

But the antidemocratic nature of the impeachment power means it should be used only against the most extraordinary threats to democracy, and only with bipartisan support.

One president in 36 being impeached sounds like a stable republic (Civil War and all). One impeachment fight in every three administrations sounds like an era of decline and fall.

Donald Trump has no business being president, in my opinion — but other voters decided otherwise. It's not hard to believe he has acted with improper motives in dealing with foreign leaders, as in much else. But there is something increasingly preposterous about America's paranoia and indignation over potential "meddling" and "interference" in our pristine political processes by pitiful thug-ocracies like Ukraine.

One thing at least is clear from all the confusing recent revelations about U.S.-Ukrainian interactions — including the machinations of Trump and his minions, the globe-trotting commercial/political escapades of Biden & Son, as well as the geopolitical maneuvers of the Obama, Bush and Clinton administrations going back to Ukraine's secession from the old Soviet Union.

What's clear is that we have here, primarily, a story about American meddling in Ukraine's affairs.

And that's a familiar story to the world. America is far and away the global leader in meddling. What other country repeatedly orders up "regime change" thousands of miles from its borders, unleashes deadly drone strikes weekly in multiple countries, dispenses military and other aid and maintains military bases — to say nothing of vast and varied intelligence "assets" — on every continent? Etc., etc. etc.

We hope habitual U.S. interference in other nations' affairs is frequently undertaken with good intentions. But let's be serious. "Meddle" is America's middle name — and most of our domestic political problems are of our own making.

So how has apocalyptic politics, including impeachment, become routine? Step one may have been the self-inflicted weakness of today's Congress; an institutional impotence that tempts it to lash out in frustration with its ultimate constitutional power.

For more than a century, Congress has steadily abdicated more and more of its intended powers as the first branch of government. It has passed increasingly sweeping, increasingly vague laws, and has acquiesced as elephantine executive agencies and activist courts have vied to become the true lawmaking bodies in the United States. Congress has also surrendered war powers and national security policy to the presidency, with precious few protests that weren't shamelessly partisan.

Increasingly unchecked and unbalanced, presidents have become arrogant, more likely to stretch boundaries to the breaking point.

Another lost force for calming and balancing American political conflict was the nation's bygone system of powerful, but internally diverse, political parties. Largely for historical reasons related to the Civil War, the South remained solidly Democratic until the 1960s, with the result that both parties long housed liberal and conservative wings that restrained one another. All that changed with civil rights, Vietnam and more. Today, both parties are ideologically monolithic and are paralyzed and provoked by "squads" and "tea parties" easily drawn to government by impeachment.

Meanwhile — through the imposition of a primary-based nomination system and campaign finance rules that impoverish parties in favor of independent entities — maverick, insurgent presidential candidacies have proliferated and succeeded. The result, again, has been overreaching presidencies and frustrated, hotheaded Congresses.

Of course, the severe ideological disuniting of America since the 1960s has combined with these structural malfunctions to lead the country down today's erratic path. A new, post-'60s progressive mind-set that at bottom sees more wrong than right with America has little in common with a more traditionalist, more complacent community that Richard Nixon called the "silent majority" 50 years before Hillary Clinton labeled them "deplorables."

But systemic, institutional causes of instability may be easier to repair than deep cultural divisions. One would like to suppose that the fading from the scene of the ever-troublesome "Sixties generation" might help in years soon to come.

But with us, remember, will go the last living memories of a less wobbly America.

D.J. Tice is at Doug.Tice@startribune.com.