Neither Bernie Sanders nor Hillary Clinton claimed victory in their post-Iowa caucus speeches last night, and the final winner likely won't be known for a while. But since the candidates will split the delegate pool, it effectively means that Bernie Sanders drew Clinton to a tie. (Indeed, a handful of the delegates—possibly enough to decide the final victor—appear to have decided by coin toss.)

Relatively speaking, that outcome has to be counted as a win for Sanders and a loss for Hillary Clinton. It's a loss that shows how weak a candidate Hillary Clinton really is.

Iowa, of course, has never been particularly kind to the Clintons. Hillary's husband Bill not only lost the caucus in 1992 to home-state Senator Tom Harkin, who came in behind both Paul Tsongas and the more than 11 percent of the state's Democratic caucus-goers who chose "uncommitted" over Bill Clinton, who was still a long-shot candidate at the time. And Hillary Clinton, of course, lost the 2008 Iowa caucus to Barack Obama, coming in third place in a near-tie with John Edwards.

But it's not just that Iowa doesn't like the Clintons.

Hillary Clinton didn't just lose—she blew a lead that as recently as November was roughly 30 points ahead of Sanders. In the middle of January, she was still running 10 to 12 points ahead.

In the end, Hillary Clinton may eke out a technical victory in Iowa, "winning" by a handful of coin-toss delegates. But the main thing that happened last night was that Hillary Clinton lost her huge lead. That's incredibly telling about her strength as a candidate.

It's often said that as voting day nears, people get more serious about their choices, and they tend to shift support to more practical candidates. Hillary Clinton ran explicitly as the practical choice for Democrats, and she did so with the financial and organizational backing of much of the Democratic establishment. And yet in the weeks and months leading up to the vote, it seems that Iowans shifted away from her—and towards a self-avowed democratic socialist Senator promising to scrap Obamacare and replace it with an impossibly expensive single-payer plan.

That tells you something about the mood of the Democratic party. Like the GOP, it is in revolt against its establishment and it is deeply dissatisfied with the political status quo, which Hillary Clinton, more than any other candidate this year, represents.

But it's also telling about Hillary Clinton's general weaknesses as a candidate: Unlike the Republican race, where establishment candidates have never had a strong foothold, Hillary Clinton had a substantial lead—and lost it as people got to know her more.

This isn't the first time something like this has happened to Clinton either. Her 2014 book tour in support of Hard Choices was supposed to be an early trial run for her presidential campaign, was a gaffe–packed disappointment, if not a flop. And early on, Clinton was widely expected to roll to victory in the 2008 Democratic primary. She blew it then too.

Hillary Clinton may well still be the Democratic nominee this year—I'd still rank her the overall favorite—and she might even take the White House. But it won't be a cakewalk, like so many insiders and Clinton allies seemed to have assumed for the last year or so. The general election is likely to be close and competitive in most scenarios, and especially with Clinton on the ticket. And that ought to make Democrats nervous: Her virtual tie with Sanders last night shows just how hard it can be for her to win a should-be easy race.