“As you can see from the chart, the percentage of Americans who had a ‘great deal’ or a ‘fair amount’ of trust in the news media has declined from over 70 percent shortly after Watergate to about 44 percent today,” writes Jay Rosen. “Why?”

He offers eight hypotheses. The first is that trust in all institutions is falling. I think that’s a big part of it. But I think #3 (”Liberal Bias”) and #4 (”Working the Refs”) are hugely important, and largely misunderstood.

The two arguments tend to be seen as opposite to one another. Either the press has a liberal bias and thus has lost the trust of a center-right, as the right claims, or it’s bending over backwards to avoid charges of bias and thus failing to report the truth and losing the trust of Americans who, say, don’t want to be misled into war, as the left claims. But rather than thinking of them as mutually exclusive claims, think of them as part of the same trend.

For the record, I don’t think the press is liberal, and I don’t think it’s easily worked by conservatives. I think the reality is more complicated and less satisfying. But let me leave that aside, as I also think the substance of the critiques are irrelevant to Rosen’s question.

Rather, I think that this poll is covering about the same period of time that political-science scholars associated with the rise of political polarization. Another way of saying “political polarization” is saying “parties became more organized and effective at communicating with their bases.” And one of the things that both parties have done is to try and weaken actors who could hurt them — for instance, the news media.

That is to say that, in terms of the loss of trust in the press, I think you should see #3 and #4 as mirror images: One is the argument the right has used to erode trust in the press. The other is the argument the left has used to erode trust in the press. Both, it should be said, have their roots in real events and real grievances. The rush to war really was an example of the media — including me, as a dumb blogger in college — getting worked. But both are also the result of organized campaigns to take those real events and real grievances and turn them into a durable distrust of the media that can be activated when convenient for the two parties.

That doesn’t mean Republicans or Democrats have stopped reading, or caring about, the news media. Indeed, the loss of trust in the press has, as I understand it, coincided with a rise in the actual consumption of news media. I think we should take that revealed consumer preference for more news and news-like goods at least as seriously as we should take these poll numbers. The parties certainly do. That’s why, rather than trying to persuade their folks to abandon the media, they have contented themselves with trying to persuade them to simply mistrust the media.