The move from the printed word to the online word is changing the news business fundamentally. And since the news is central to our political system, the trend toward news online is changing how our democracy works as well. We’re not all news junkies, but we’re all citizens, so this matters.

Our republic was established with freedom of the press as a cornerstone; the Founding Fathers assumed it, the First Amendment enshrined it, and for the most part the Supreme Court has protected it. While our press is far from perfect, anyone who has lived abroad will tell you that the American press is more independent and more professional than most others around the world.

By “independent,” I mean free of political influence and commercial pressure. By “professional,” I mean pursuing aggressive but evenhanded inquiry, verifying facts and statements, and explaining what sources were used and how judgments were reached so the reader can evaluate what is being offered.

Last month the Pew Research Center for the People and the Press published a survey that suggested public belief in what the press reports has declined significantly over the past 10 years.

The proportion of Americans finding the news media “believable” dropped from 71 percent to 56 percent. Some sharp differences lay hidden in those figures: Republicans became much more skeptical of news organizations during the past decade, except for Fox News and local TV news, while most Democrats still found most news outlets believable except for Fox News.

Does all this mean that the news media are less credible, doing a less independent and professional job? Does it mean they’re still doing an independent and professional job, but the public doesn’t believe what news organizations are reporting? Does it mean political leaders are dissembling more, and in reporting all this dissembling and manipulation, the press itself is found less believable? Or do the Fox News figures indicate only that the body politic is becoming more polarized, and the factions believe those with views different from their own even less than they believe ones with views similar to theirs?

There is plenty to worry about in any of these possibilities. An independent news media is the indispensable oxygen of democracy. You would be hard- pressed to name a democracy that remained one very long without an independent press to report on politics and the government “without fear or favor,” as the saying goes. The two largest democracies in the world — India and the United States — are still democracies in part because they have an independent, at times raucously outspoken, press.

But what good is an independent press if increasing numbers of citizens don’t believe it? Basic confidence in the integrity, independence, and credibility of at least some of the media is a prerequisite if the press is to serve as the oxygen of democracy. And the clear trend over 10 years is that fewer and fewer of us believe what the media report. Since online news makes it much easier to find outlets that paint the world the way we’d like to believe it is, the potential for even more fragmentation and distrust would appear enormous.

What would our political system look like if, say, three-quarters of our citizens did not believe what most news outlets were telling them? If they had the same contempt for most news organs that Russians used to have for Pravda? That might reinforce trends in our society toward believing in conspiracies, or feeling the need to take matters into one’s own hands rather than accepting the decisions of government. In a country where weapons are easy to get, this is not a comforting thought.

If you think we’re divided and in gridlock now, the direction of the trends in this research suggests we ain’t seen nothin’ yet.

Peter Goldmark, a former budget director of New York State and former publisher of the International Herald Tribune, headed the climate program at the Environmental Defense Fund. He wrote this for Newsday.