(CNN) It's one week until Hillary Clinton's 2016 memoir "What Happened" is officially released. But, in an excerpt that made the rounds today , Clinton writes critically about her 2016 primary opponent Bernie Sanders. Clinton makes the case that Sanders damaged her chances of winning with his pie-in-the-sky proposals that pleased liberals but could never actually become law.

So, is she right? CNN's Greg Krieg and I spent the afternoon exchanging emails about that very question. Our conversation -- edited only lightly for flow -- is below.

Cillizza: All right, Greg, We're getting bits and pieces of Hillary Clinton's book about the 2016 election as we get closer to it hitting bookstores (are they even a thing anymore?) next week. The new nugget features Clinton running down Bernie Sanders for his primary challenge in 2016.

The part I cared about was where Clinton compares Sanders to a one-upper. That no matter what she proposed, he would propose something even more appealing to the party's liberal base -- entirely without any consequence.

Recollects Clinton: "We would promise a bold infrastructure investment plan or an ambitious new apprenticeship program for young people, and then Bernie would announce basically the same thing, but bigger. On issue after issue, it was like he kept promising four-minute abs, or even no-minutes abs. Magic abs!"

To my mind, she's not wrong!

Clinton was forced to be mindful of how the positions staked out in a primary would impact her in a general election. Sanders, who no one -- including him! -- thought could or would win, had no such constraint. He could propose whatever he wanted in a largely consequence-free environment while she lived in an all-consequences, all-the-time environment.

Sanders was running a cause. Clinton was running a campaign.

Tell me how I'm wrong.

Krieg: Let me start by saying, the timing of this book is truly remarkable. I know these things are set way in advance and wouldn't be shocked if Clinton herself -- despite all the frustrations we've read about in just these few pages -- might wish this debate, both ours and the one now blazing on Twitter, could be put off a bit.

Or not!

Anyway, I'm struck right off the bat by how little nuance there is in Clinton's assessment. For such a smart, savvy and accomplished person, she comes off as weirdly blinkered. These paragraphs are pretty narrowly composed and make no real account for why Sanders was so popular. Perhaps it's comforting to dismiss his popularity and, implicitly, the desires/frustrations of his supporters, as being rooted in the desire for free ponies or "magic abs." But that really undersells the issue at the heart of this.

Sanders was, of course, coming at this campaign from a very different angle. By his and his aides' own admission, they were surprised at how quickly a movement-based candidacy turned into an electorally viable one. But even then, he was pitching a fundamentally different view of politics. Now, you can dismiss that as unreasonable or unlikely to happen, but it's a losing strategy, in broad terms, to quit the conversation there.

Did America want a pony? Perhaps. Though I'd say Americans were and are frustrated by their debt and economic inequality and medical bills, etc. Essentially saying that their desire for relief was wishful (and frankly, silly) puts a pretty fine point on her shortcomings a candidate.

Cillizza: Look. I love a free pony as much as the next guy, but you make a fair point.

I think one of Clinton's biggest problems in the race was that she never understood that Sanders' appeal wasn't totally about his proposals -- which weren't radically different than hers -- it was about his tone and willingness to confront Republicans at all times and on all fronts.

Her political background was forged in the 1980s and 1990s -- when bipartisanship was something to be aimed at. That wasn't the mindset of the Democratic Party, whose nomination Clinton was seeking. They wanted confrontation. They viewed the GOP worldview as not just wrong but immoral. They didn't want carefully poll-tested policies designed to barely keep them on board while also peeling off moderate Republicans.

Sanders intuitively understood that because he has made charging at GOP-constructed windmills his life's work. All the way to the end, Clinton never grasped what Democrats really wanted from her.

I think the tendency to dismiss Sanders in the book is representative of the fact that she still doesn't get that reality.

ALL of that said: I still think running a campaign against a candidate running a cause is really, really hard. I would be fascinated by what would have happened if, after his New Hampshire victory, Sanders had been able to score a few more wins in big important states over that next six weeks. It might have changed the perception of the race -- and forced Sanders and the Democratic Party to come face-to-face with the real possibility that he might be the nominee.

Krieg: Last things first. I agree entirely -- with you and Clinton -- that Sanders did not have as fully developed of a policy portfolio. During the debates and in some interviews during his early 2016 surge, his lack of clearly defined foreign policy ideas sometimes made plain his shortcomings. As it happens, part of the reason he didn't win much in those post-New Hampshire weeks was that he didn't have the infrastructure or the time to develop a compelling enough message to win down South. (And even with more time, winning there was certainly no guarantee.)

I also agree that, on balance, Sanders' proposals weren't too far from Clinton's. The debate over higher ed is a great example. Clinton wanted debt-free college. Sanders went a bit further, suggesting a tuition-free approach. They eventually hashed out a compromise plan. This is why so many progressives, in the days before the election, were confident of having a seat at the table in a Clinton administration.

But again, the fundamental issue here -- as you note -- is that Clinton didn't then, nor does she now, seem to accept the legitimacy of the Sanders wing's underlying argument. Which is, (overly) simply stated, that the country has -- over the last 30 or 40 years and with the Democratic Party's acquiescence -- been moving away from public control of public goods. For example: Those "market-based solutions" that seem to do more for the market than those looking for solutions.

This was always tough and clearly annoying to Clinton. She's been in the arena; Sanders was a mayor in Vermont, then a back-bencher in Congress. But -- and look to the UK and Jeremy Corbyn for further evidence here -- that is not enough of an argument for many voters. In fact, lots of Sanders supporters will tell you that his unwillingness to play ball and make compromises they view as having damaged the working class is not a bug, but a feature piece of his appeal.

Here's a question: Where are you on the "his attacks caused lasting damage" argument? A lot of Sanders people will say that, if anything, he pulled punches.

Cillizza: Absolutely not!

I agree with Sanders' people who say he pulled punches. He refused to ever talk about her email server which was, literally, a hanging curveball that he could smash out of the park. And, on her speech-giving to massive corporations -- including Goldman Sachs -- Sanders went WAY easier than he could have if he wanted to portray Clinton as a corporate shill.

Hillary Clinton lost because she was never the "heart" candidate of the activist base, because she never grasped what the email server really meant to people (that the Clintons think the rules don't apply, that the Clintons think they are deserve different treatment), because of James Comey announcing the re-opening of the email investigation, because of WikiLeaks/Russia and mostly because she was the status quo candidate in a change election. But, she definitely didn't lose because of Bernie Sanders.

One last thing that this conversation has got me to wondering about: Is there going to be a candidate from the "Clinton wing" of the Democratic party in 2020? Joe Biden? Can he qualify? He never loved or ascribed to Clinton's sort of politics -- and is much more willing to speak out than she ever was. But, if it's not Biden, then who is that candidate?

Krieg: One other thing on the Clinton-Sanders dynamic before I get to the (fun) 2020 stuff. Clinton here notes -- correctly! -- that she had better fleshed-out policy positions. But I think what frustrated people on the left, and certainly some of her most ardent supporters, is that she did not always center them during her campaign. These things are visceral, and always have been, so when you reply to some questions with, "Go look on my website," that's going to frustrate people.

Ironically, what was on Clinton's website would have appealed -- tweak here, tweak there -- to a whole lot of Sanders supporters. Obviously there was an element within his support that, on a personality level (heightened in some cases by very real sexism), was never going to give her a look. But there were others, I think, who had/have room in their hearts for both Bernie and Hillary! (In fact, I'd say that's the majority of Democrats.)

As for 2020... oy. A few months ago I'd have said this primary is 100% going to boil down to a Clinton winger vs. a Berniecrat. Though I think some people will see it that way no matter what, as we go forward, I'm thinking the Democratic Party is going to square this stuff away before then. Maybe not in terms of its larger message, but as it relates to a national candidate. (See Kamala Harris, and surely others, co-sponsoring Sanders' single-payer test bill. Or Elizabeth Warren, who basically everyone in the party and on its left could rally behind right now.)

So, could it be Biden? I doubt it. People who tout him, I think, believe that Clinton's loss was mostly about personality and that Ol' Joe could run on about the same policy and win over the working class voters she lost. My bet is that a group of younger candidates with fewer attachments to the '80s and '90s will emerge.

One caveat: Sanders himself. If he runs, which I personally don't think he will do, it upends all of the above. The 2016 scars come right back out. And maybe Biden does get drawn back in.