Music superstar and political activist John Legend sat down with CNBC's John Harwood to discuss a range of topics, including whether Democrats should run a celebrity against President Donald Trump in 2020.

John Harwood: There are some people who are making the argument that Donald Trump has changed the political rules such that you need somebody with celebrity star power to compete. So, people talk about Oprah Winfrey, for example. Do you think a celebrity candidate is a good idea and whether now or in the future, is this something that you entertain at all?

John Legend: I don't want to be president and I will never run for president. I know that for a fact.

Harwood: How do you know that?

Legend: I just know I won't. But, I do believe sometimes there's a place for people who already have name recognition and already loved by the people to run for office. It's funny, the Republicans hate when celebrities talk about politics, but they've been the ones that have elected all the celebrities. They've elected Donald Trump and Ronald Reagan. On the left, we've elected usually career politicians and people that are a little more wonky. So, there's an argument to be made that the left shouldn't always go for the wonky person and get somebody who is more of a celebrity, but honestly, I feel like the Trump administration is an argument against that.

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He won, but once we see how he's governed, he's not very good at actually governing and understanding how to use the leverage of power very well, even understanding the basics of policy. I would like my president to know the issues really well. I'm not saying a celebrity can't know them, but I would like someone that understands how government works and can actually be effective in the office.

Harwood: So, you're not trying to draft Oprah into the 2020 race?

Legend: The thing is, she's brilliant and she probably could learn anything. But that's not what she does right now, and I'd be hesitant to elect anybody that has to learn on the job about how the government works, and that doesn't have some really well-formed ideas about what they want to do in office.

Harwood: I have heard some people say, looking to the future, say that 2020 may not be so smart for Democrats to have an African-American presidential nominee this time. Do you agree with that or not?

Legend: I don't think it matters as much what the demographic of that person is. It's going to be the quality of that candidate. So, are they speaking to issues that people care about? Are they able to spar with President Trump, because he has a unique kind of campaigning style and debating style. You have to be tough, and you have to be witty, you have to be quick on your feet, and you have to be a great communicator and really a great marketer like he is to compete on that level.

I think my kind of metric for how I'm going to get engaged with the primary process is, do I see a candidate that stands out when it comes to their ability to challenge President Trump?