WASHINGTON — New York Mayor Bill de Blasio is urging Democrats to "throw away conventional wisdom" and run on "big goals."

As food for thought, he offered two of his own first-term policies: instituting universal preschool and ending the police's stop-and-frisk policy.

It's a message he’s carried outside the confines of the five boroughs over the last few years. The mayor spoke at the Center for American Progress on Tuesday, a daylong event that featured a number of candidates viewed as possible 2020 presidential contenders. de Blasio has visited Iowa touting his message of "progressive economic populism," keeping his own profile in the mix.

NBC News caught up with de Blasio after Tuesday's speech to discuss where Hillary Clinton and Barack Obama went wrong, why Democrats should run on taxing the rich, and whether New York bears some blame for giving the world Donald Trump. Here's our conversation, edited for length and clarity.

NBC News: You spoke about the importance of having big progressive ideas to run on. What should be the headline policy?

De Blasio: Tax the wealthy.

This is the great dividing line. If you are willing to say out loud we need to tax those who have done very well to help everyone else, that proves to people both intent, but also typically some sense of courage.

When I did my Pre-K initiative, it was the signature of my 2013 campaign. In anticipation of announcing that there would be a tax on the wealthy to achieve Pre-K, we had an internal discussion on the team and some of us said that it's likely a certain number of our supporters will really take exception to this. And right on cue, I gave a speech at the Association for a Better New York and within 24 hours, five members of my finance committee had resigned. They were good people, but they philosophically were rabidly against taxes on the wealthy and they happened to be a little better heeled.

American working families are going through a lot. If Democrats can plausibly say, 'Here's what we're going to do to lighten your burden' and we are consistent about it rather than this grayness which seems to afflict our party so often, I think it will be very appealing to people.

In the past that approach has often been dismissed as redistribution. Is that a label you think you should embrace?

I have no problem with the charge of being redistributionist. I don't know of any time in history when people have been uncomfortable with that.

Think about it: The things we do that are universally loved, like Social Security, clearly have an element of that. There is a deep yearning for better schools — that implicitly is taking money and applying it to a broader public good. There's a deep understanding that the wealthy have done better and better largely due to government policies.

We have to get out of that past set of assumptions that basically drove us into the ground and be proud of who we are. Most Democrats are redistributionist and that’s fine.

Some Democrats argue that the lesson of Trump is that they need to go big and bold, but their past mistake was saying how they would pay for it. Instead, just say 'Growth will pay for it' or 'Just add it to the deficit,' after all that's what the other side has done.

I think if you say, 'We'll tax the wealthy' you are both being honest about how you'll pay for it and about real power dynamics. It shows a willingness to stand up for people’s interests against those who hold all the power right now.

I think Trump ironically presented himself as taking on the status quo and taking on the elite — then he drained the swamp right into the Cabinet. He didn't actually intend to take on the elite and powerful interests, but his rhetoric and what appeared to be a set of policies were aimed in that direction.

What if you did the real thing? What if you said we’re going to challenge the power structure, we're going to challenge the elite, we're going to challenge the wealthy and actually use that money to help people and here’s how? I think a lot of people would respond to that.

There's a lot of conversation now about how Democrats are in a bubble and confined in big cities. Do you think somebody like you, from New York, should be leading Democrats into the future? Or should there be more voices from rural red America?

I have a totally contrarian theory on this. First of all, we're so much more of a homogenous country than we were a few decades ago. There's much more of a national culture: People live in different parts of the country much more, travel, have family all over. I feel like growing up in the '60s and '70s it was a much more deeply regionalized country. Now it's hyperconnected and obviously the digital age has added to that as well.

I always talk about the last days of 2016 and the two-minute ads — and as a Democrat I say this with a lot of pain. The Hillary two-minute ad was pleasant and hard to define, the Trump two-minute ad was urgent and populist and if I didn’t tell you the candidate and just played you the script and the music and all, you’d probably say, 'Oh, that's the Democrat.'

Who is more coastal, city, materialist, superficial, etc., than Donald Trump? And yet he appealed to the heartland because he was talking about something they cared about.

Where does Obama fall in this category? How do you explain how he wasn’t able to build a third term, essentially?

I think he had a vision of trying to reconcile the nation and bring red and blue together, which was noble. But I imagine he would say it quickly became impossible. Unfortunately, I think it took some of the wind out of the sails out of defining what the party was at the same time. And obviously he was such a huge personality that a lot revolved around him when what we really needed more than huge personalities was a single vision and a single message. That wasn’t the focus of his team. He's not alone: It's clear Bill Clinton wasn’t focused either on the grass roots of the party and the state legislatures, etc.

Is there an element of New York politics or New York culture that you recognize in Donald Trump that you think has national appeal?

I think there are elements of New York culture and New York politics in Donald Trump that are a bad thing and should be stamped out.

There's probably no place in America where there’s more opposition to Donald Trump than New York. Interesting statement that his own city is the wellspring of opposition to him. They voted 80 percent against him in the general election.

But does Trump come out of New York in some very troubling ways? Sure. He comes out of tabloid culture, he comes out of the materialism, he comes out of that kind of superficial Wall Street and fashion culture, he's connected to all of that stuff in a way that is kind of damning, you know, that is something we need to address in our city.

I think there’s a sort of correction occurring and that New York City does not buy into that culture that produced Donald Trump and I don't think it will be repeated. But unfortunately that culture which was, and which still exists to some extent, birthed something really problematic for the country. There's no question if he came from somewhere else he’d be a different person.

I’ll ask the question every political reporter is contractually obligated to: Are you thinking of running for president? Who would you like to see running?

I'm mayor of New York City, that's what I'm doing, that's the only plan I have. And I think there's a lot of great progressives right now, which encourages me, but my focus and everyone's focus should be 2018. The starting gun is not until we get through the midterms.