Why is Donald Trump declining in the polls? The media strike again.

[Commentary] After over two months of growing poll numbers, Donald Trump has suddenly experienced a notable drop-off -- visible in the Pollster polling averages as well as the Real Clear Politics average. So why are Trump’s polling numbers declining?

As I’ve argued before, changes in people’s preferences almost always require changes in the information they’re receiving. For Trump, media coverage has been crucial in motivating his surge. Now, media coverage is arguably motivating his decline. There is a correlation. An initial surge in news coverage after Trump announced his candidacy on June 16 creates an initial surge in polling. Then, further increases in news coverage coincide with increases in Trump’s polling numbers -- likely in a self-reinforcing cycle. But right before his apparent decline in the polls, there was a decline in his share of news coverage. Just as news coverage helped create Trump’s surge in the polls, it appears to be helping create his decline. We’ll see if that continues.

[John Sides is an Associate Professor of Political Science at George Washington University. He specializes in public opinion, voting, and American elections]