We journalists seldom underestimate the importance of our profession to American democracy. And we're not excessively critical of ourselves when it comes to diagnosing the causes of our institution's problems.

That said, the damage done to American journalism and its standing with the public in the era of Trump and Twitter — however much of that harm has been self-inflicted — really could prove perilous for the nation.

Such fears are fueled, at any rate, by a pair of striking surveys from Gallup in recent months.

In September, Gallup released results of a nationwide poll asking Americans "how much trust and confidence [they] have in the mass media — such as newspapers, TV and radio — when it comes to reporting the news fully, accurately, and fairly." They've been asking this question for almost 50 years, annually for more than 20. The trends are not encouraging.

In the mid-1970s, overall confidence in journalism peaked, Gallup says, with 72% reporting "a great deal" or "a fair amount" of trust. Vietnam and Watergate had undermined faith in government, and an intrepid press had exposed deceit and error.

By the late 1990s, amid Clinton scandals, talk radio's heyday and the internet's first wave, trust levels had fallen to 55%. They drifted lower from there, through the increasingly polarized Bush and Obama eras.

This year, overall trust in media stands at 41%, Gallup reports.

Much worse, 28% report no trust at all in American journalism — seven times the level of 1976.

But even that's not the most worrisome part. Gallup's breakdown of trust levels by political affiliation shows that confidence in the American mainstream press has become more powerfully correlated with ideology than ever before.

In the late 1990s, as today, self-described Democrats had the most trust in news media and Republicans the least, with independents in between. But the gaps 20 years back were modest — less than 10 points in some annual surveys. Democrats' trust levels moved gradually lower during the Obama years, while Republican trust dropped further, widening the confidence gap. But partisans' attitudes were moving in the same direction.

Then came Trump.

Republican trust has plunged by half in the past four years, to just 15%.

What's more remarkable is that Democrats' trust level has soared at the same time — from 51% during the 2016 campaign to 76% last year.

The allegation of "liberal bias" in the mainstream press is nothing new, of course. But the trust gap that has opened up today is unprecedented. With Democrats in this survey (and other recent polls tell a similar story) five times as likely as Republicans to trust what they hear or read, it's clear that mainstream journalism is simply coming to be perceived as a messaging arm of modern progressivism.

It's the satisfied liberal customers, even more than the grumpy conservative ones, who reveal this.

The danger is that sane debate and compromise on public policy will be hard to recover if the nation has lost all common sources of credible information.

What has happened most recently, of course, is Trump and all that he has wrought. Many presidents have had stormy relations with the press. None has begun to equal Hurricane Donald, whose crude and unending denunciations of the "fake news" media may have had some effect on public perceptions.

But along with "Trumpism" — all the unprecedented barbarities of this presidency — the press also suffers from what is better called "Trump-itis." It's an inflammatory overreaction that has inspired obsessive and implacably hostile coverage of a caliber never really seen before.

Meanwhile, something else may also be at work, more subtle and perhaps more lasting. Long before Trump's political debut, the press broadly defined had been in the process of reconsidering and relaxing its stuffy old standards of impartiality and "objectivity."

The "fairness doctrine" had been lifted from broadcasters, and scalding political talk radio had flourished.

Cable television brought cable news networks and more hot-tempered, one-sided partisan gab. Fox, MSNBC and CNN have today become emblematic redoubts of political tribes.

Newspapers added more "voice," too, especially in online offerings, and loosened standards for anonymous sourcing.

And everywhere, with Trump's arrival, longstanding hesitations about labeling statements "lies" or "falsehoods" were discarded.

Note that Gallup's survey didn't ask respondents particularly about newspaper opinion pages or TV commentators. They were asked whether they trusted "reporting [of] the news."

Many pressures driving media trends are economic and technological. Newspapers were born as political party organs, the "partisan press." The news "business" began as a kind of sideline — selling ads to defray costs. But in time, shrewd publishers realized that by jettisoning one-sided bias they could appeal to a broader slice of the population, dominate local markets, and sell more papers and more ads. And so the professional, evenhanded press arose, not least as a business plan.

In recent decades, the internet finished the job of flooding the modern information marketplace with so many voices and sources that the historic mass-market business model for news has, well, changed. News providers may be discovering a path to survival in resurrecting the older "partisan" model — fragmenting the market and giving smaller audiences the precise flavor of content they prefer.

And of course Trump is the perfect subject matter for nuance-free news.

The partisan trust gap Gallup found for the traditional media may simply be a symptom of this economic process. Impartial journalism may be what the public truly needs, but not what the modern marketplace rewards any more.

Consider that an August Gallup survey shows that Americans' trust in internet news has risen from 25% in 1998 to 40% today. But that's still far below trust levels for local TV news (74%) or local newspapers (67%).

The awkward thing is that the internet is the only source that has seen dramatic increases in regular use over the past two decades. Its use every day or several times a week has rocketed from 12% of adults in 1998 to 64% today. Meanwhile, the best trusted sources (local TV news and local newspapers) have seen regular use fall sharply — by more than half in the case of newspapers (though use of newspapers' and stations' online sites mitigate these declines).

Undoubtedly, a generational effect is at work here, with younger adults relying on internet news far more heavily than their elders.

But one fears this is simply another trend leading toward more and more Americans having less trust than they used to in the news sources they use the most.

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