In the — gulp — almost 20 years that I have been covering politics and political campaigns, I've never, ever seen a candidate anything like Donald Trump. Say what you will about the messenger — a Democratic senator called Trump a "Cheeto-faced short-fingered vulgarian” on Thursday — but it is impossible to deny the power of the message that Trump embodies for a big chunk of the population in this race.

I am convinced that whether he wins or loses in 47 days, we will be talking and writing about what Trump meant for years (and maybe decades) to come. Given that, I spend part of most of my days trying to better understand how Trump's movement came to be and whether we should have seen it coming long before most of us did.

This chart — taken from Democratic pollster Peter Hart's breakdown of the latest NBC-Wall Street Journal national poll — seems to carry some major clues about Trump's appeal. It documents how people have responded to a question of whether they think the country is headed in the right direction or is on the wrong track.

It has been more than 12 years since more people said the country is headed in the right direction than said we are off on the wrong track. And in the years since 2004, the wrong track number has soared — hovering at or above 60 percent for much of the past decade. (President Obama's election in 2008 briefly dropped the percentage of people who thought the country was on the wrong track to 50 percent. But that was a short-lived dip.)

That's a very long time for a very large chunk of the public to believe that things in the country simply are not going well. Our long-standing national pessimism appears to be one of the few things not wholly dependent on partisanship; people thought things were going badly under President George W. Bush and they think the country is headed in the wrong direction under President Obama.

The reasons for this are many. The (still) slow economic recovery from the problems of the early 2000s. A growing sense — fueled by the Wall Street collapse — that the gap between rich and poor is growing wider and wider. An ongoing anxiety about what the United States' role in the world is — and what it should be. The perceived erosion of the American Dream. And a thousand other things.

But the broader point is that people don't feel terribly optimistic about where we are headed. And they haven't for a very long time.

It's not hard to grasp then how a candidate insisting that the country is crap and will remain crap unless major changes — most notably electing him president — are made and made soon, is doing so well.

Trump was initially dismissed as a showman whose dark vision for the country would never sell to a Republican electorate raised on the sunny vision for the country of Ronald Reagan. But as the chart above shows, we haven't regarded ourselves as that shining city on a hill — or had much hope we would become it — for a very long time now. The average "right track" number has averaged 28 percent over the past six years. That's stunning.

In an environment of pessimism like this one, a man willing to acknowledge how bad everything is and promising to fix it all with a snap of his fingers has lots and lots of appeal to voters. Especially when that person is running against someone largely promising to maintain the status quo.