The good news for Bernie Sanders is that he won Wisconsin last night, and won it by a very healthy 13-point margin. The bad news for Sanders is that in doing so he likely fell even further behind the pace he needs to capture the Democratic nomination.

With seven of the past eight states to vote in the Sanders column, Berners feel they have momentum on their side. But the truth is that little has changed in terms of the underlying demographic divides in the race — young and white Democrats like Sanders; older, black, and Latino Democrats like Clinton. And relative to its demographics, Sanders simply didn't do well enough to catch Clinton.

The state of the race pre-Wisconsin

Before Wisconsin voted, Sanders was already well behind Clinton in the delegate race. That means that to beat her, he needed to not only beat her in the remaining states but beat her badly to cut into her delegate lead. How badly?

Nate Silver produced a great series of estimates based on the demographic composition of each state. The result was not a likely scenario in which Sanders caught Clinton, but rather the most plausible one he could think of. It gave Sanders a target of securing 50 of Wisconsin's 86 delegates by scoring a 16 percentage point margin of victory. Ambitious, but doable.

He came close, but he didn't do it. And that means he'll have another delegate or two he needs to add in future races.

The map is about to get way tougher

To Sanders fans, the fact that he's won seven of the past eight contests feels like he has enormous momentum in the race. To the demographically inclined, it just looks like a coincidence.

Because the five largest states — California, Texas, New York, Florida, and Illinois — all have above-average black and Latino populations, most states have below-average black and Latino populations. Because of that, Sanders is well-positioned to win a large number of states that have few residents and assign few delegates. He happens to have benefited from a small run in the calendar that featured a whole bunch of these states.

Next up comes Wyoming, which will make it eight out of nine. But then comes New York, which happens to allocate more delegates than Wyoming, Wisconsin, Washington, Hawaii, Alaska, Utah, and Idaho combined.

New York is 17.6 percent African-American (versus 6.6 percent for Wisconsin) and 18.6 percent Hispanic (versus 6.5 percent for Wisconsin). Relative to that much more diverse electorate, it's not good enough for Sanders to narrowly edge out Clinton. According to Silver's math, he needs to beat her by 4 points to net enough delegates to stay on track — and that's even before he fell a delegate or two short in Wisconsin. Right now he's down 10 points.

The media is biased — in favor of Sanders

To Sanders fans, this naysaying is just more evidence of the anti-Bernie bias in the media.

The truth is exactly the opposite. The media has a systematic self-interested bias toward exaggerating how close the race is. Sanders supporters are a minority of Democrats, but they are still a large number of people, and they avidly read and share content about Sanders's big fundraising hauls and his wins in low-population states.

Television networks want people to tune in to their debates and town halls, which they are much more likely to do if they think something is at stake. And Sanders's big fundraising has been transformed into big advertising dollars, which is literally money in the pockets of media companies.

The media loves Bernie Sanders!

And so do millions of voters. But somewhat more voters like Hillary Clinton, which is why she's been ahead of him in national polls from the beginning and why he keeps falling further and further short of the delegate totals he needs to win.

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