Hillary Clinton's lead over Donald Trump was about five points in a Suffolk University-USA Today poll released Monday. That's about in line with the recent RealClearPolitics polling average, which estimates Clinton's lead at four-and-a-half points in all of the various recent surveys.

Buried in the cross-tabs of the Suffolk-USA Today poll, though, is an interesting bit of data. The pollsters also asked people which news network they trusted the most, which allows us to see how fans of one network versus another view the two major-party candidates for president.

People who trust MSNBC the most were more likely to back Clinton, by a 77-point margin. CNN-watchers were also heavy Clinton backers, by 55 points. Fans of the major traditional networks all preferred Clinton, too, by 35-, 20- and 38-point margins for viewers of ABC, NBC and CBS, respectively.

Viewers of Fox News, as you might expect, were the only group to prefer Trump, and did so by a 71-point margin.

So how is Trump within four points if people who watch every other network prefer Clinton? Because way, way more people watch Fox.

There is a correlation between watching Fox News and backing Trump, but it's not clear if there's causation, or which way that causation might point. Fox News is understood to be a conservative counterweight to the traditional "liberal" media, meaning that many Republicans chose the network as their preferred outlet well before the Trump era. (In the Suffolk poll, 56 percent of Republicans pick Fox as their most trusted network, to 5 percent of Democrats and 20 percent of independents.) In the Trump era, the Republicans who were already watching Fox announce that they support Trump.

As it stands, two-thirds of Trump's support comes from people who say that Fox News is their most-trusted news source, to a fifth of Clinton's that comes from MSNBC.

What would likely happen if you took away Fox News is that the red bars for the other networks would grow larger. (If you took away MSNBC, the blue bars would grow larger, but not by as much.) The story is likely one of symbiosis more than of either Fox or Trump making the other happen. But that symbiosis is much stronger than one might have assumed.

This post has been corrected. The original version left out CNN due to my oversight, which annoys me.