Here's how Americans rank the 2020 presidential candidates on the political spectrum

Matthew Putney/AP

2020 Democratic presidential candidate Sen. Bernie Sanders speaks during a rally at the Iowa state fairgrounds in Des Moines, Iowa.

• By a wide margin, Americans believe self-described democratic socialist Sen. Bernie Sanders is the most liberal 2020  candidate in the Democratic field, according to a recent INSIDER poll. 
• Sen. Kamala Harris, Sen. Cory Booker, former Secretary of Housing and Urban Development Julián Castro, and Sen. Elizabeth Warren are perceived as the next most liberal candidates.
• Former Vice President Joe Biden is perceived as middle of the pack on ideologically, with Rep. Seth Moulton of Massachusetts perceived as the least liberal. 
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Former Vice President Joe Biden recently claimed to have "the most progressive record [of] anybody running" in the 2020 Democratic presidential primary.

Sen. Bernie Sanders, the Vermont democratic socialist, begged to differ.

"I don't think there's much question about who's more progressive," Sanders said of himself and Biden. 

But what voters think can differ from the candidates' opinions of their own ideology and legislative record.

In that spirit, INSIDER asked Americans to rank the 2020 presidential candidates based on ideology.

Once the poll respondents indicated which of the candidates they had heard of, we followed-up by asking them to "Please rank the following candidates based on how politically left you perceive their politics to be, with the contender in the first (1) position being the most liberal and the contender in the highest-numbered position being the least liberal."

Americans believe Sanders is the most liberal candidate in the Democratic field - by a wide margin.

Sen. Kamala Harris, Sen. Cory Booker, former Secretary of Housing and Urban Development Julián Castro, and Sen. Elizabeth Warren are perceived as the next most liberal candidates.

Biden was ranked right in the middle of the pack, while Reps. Seth Moulton, Eric Swalwell, John Delaney, and Tim Ryan, and Sen. Michael Bennet are seen as the least liberal candidates in the field.

Since not every respondent knew all the candidates, or necessarily knew a lot of information about the candidates they had heard of, we used a technique called maximum likelihood estimation (MLE) to generate scores for individual contenders.

Conceptually, MLE is similar to how statisticians are able to use strength of schedule to compare two sports teams that haven't played against one another. 

Here's the ranking of presidential candidates, from least to most progressive, according to Americans: