(CNN) A look at the policy positions of the 2020 Democratic field suggests this group of candidates and potential contenders is further left than those running in previous cycles.

In past years, you might not have expected, for instance, that so many candidates would sign on to Medicare for all or the Green New Deal

But are the Democrats running for president this year truly further to the left than other recent cycles? A look at the candidates who have been members of Congress suggests that they are, as a group, considerably more liberal.

We can see their liberalness in their voting records. To be clear, there are many ways to calculate a candidate's ideology (as we'll talk about a little below). Depending on which one you use, you can come to a different conclusion about how liberal someone is.

Still, voting records are among the better methods and easiest to calculate.

The website Voteview tracks the roll call votes of members of Congress. I've taken a specific metric on their site that allows members of Congress to become more or less liberal over their careers and averaged the vote records for each candidate over the last three Congresses before their presidential run. I've also rescaled the scale to make 0 most liberal and 100 most moderate.

Hillary Clinton, John Kerry and Barack Obama all had scores between 63 and 66 using this methodology. This score put them roughly in the middle of their party's senators' average score.

This year the current or past members of Congress who have either declared their presidential candidacy or have formed an exploratory have an average score of 48. That is, they are considerably more liberal as a group than the past nominees or the average Democratic member of Congress.

Interestingly, the roll call votes do paint a picture of certain candidates racing to the left, despite being somewhat more moderate in the beginning of their careers.

One such candidate is Gillibrand, who many detractors argue has flipped-flop over her career . There numbers show that Gillibrand has shifted. When she was a House member from upstate New York, her score was considerably more moderate (82) than it has been over her last three terms in the Senate (35).

Part of Gillibrand's movement is no doubt because she is now representing the much more liberal state of New York in the Senate than her more conservative congressional district. Her shifting positions are not just because who she is representing has changed. In her first four years in the Senate, Gillibrand scored towards the middle of the Democratic caucus (58). In the last two years, Gillibrand was far more liberal (15).

Booker seems to be moving to the left as well. A number of people on the left view him with some suspicion because of his prior support for more moderate positions (such as defending private equity ). Indeed, his voting record score in his first two years in the Senate was much more moderate (53) than it was in the last two years (36).

In fact, a different system for judging ideology suggests Booker has moved even more to the left. We can estimate a candidate's ideology based on who gives money to candidates. Back in 2014, numbers from the Database on Ideology, Money in Politics, and Elections showed that Booker's donors were more moderate as a whole than all current 2020 candidates but John Delaney's.

Why are Democrats as a group running to the left? They seem to be responding to a Democratic electorate that is, at a minimum, describing themselves as more liberal. The Pew Research Center found that 44% of Democratic voters (including those independents who lean towards the Democratic Party) called themselves liberal. Back in 2004 , just 30% of this group said they were very liberal.

Candidates moving to the left may be making a mistake, however. The majority of Democratic voters still identify as moderate (54%), and Gallup finds that that at least in the abstract a majority of Democrats (54%) want their party to become more moderate instead of liberal. Part of that may be that be they think a moderate candidate is more electable, which is what Democratic voters prize most in a nominee at this point.

Of course, it could be the case that none of this ideologically positioning ends up mattering too much for vote choice. Voters make their decisions based off a slew of factors including simple candidate likability.

Still, the fact that this field is further to the left than previous nominees is important. Studies indicate that presidents are likely to at least try to keep their campaign promises.

That is, there does seem a better chance than normal that we'll end up with a more liberal president than we've seen in recent years if the eventual Democratic nominee wins in the general election.

If Klobuchar or Joe Biden (who is still weighing a presidential bid) win the primary, however, the Democratic nominee could end being more moderate than previous years.