Sen. Bernie Sanders is now leading the Democratic field in both a standard poll — and a “ranked-choice” survey designed to identify who a majority of people ultimately prefer in a crowded field.

According to an online national poll sponsored by FairVote and conducted by SurveyUSA, Sanders comes in first in both surveys. Former Vice President Joe Biden, meanwhile, comes in second and trails him narrowly in the two polls.

The results point to Sanders’s growing strength in the Democratic field: He’s recently won back-to-back victories in New Hampshire and Nevada, and has emerged as the delegates frontrunner. The polls indicate that he is both the first choice of a plurality of voters, as well as the second choice for a sizable fraction.

Here’s how the ranked-choice tallying works: Rather than just selecting their top choice, voters are asked to rank several candidates in order of preference. Then, when the votes are counted, if no candidate has accrued more than 50 percent of the vote, the candidate who has the fewest first-choice votes is removed. Those votes then go to each voter’s next ranked choice. This process is repeated until one candidate secures a majority of the vote.

A person whose top choice was Rep. Tulsi Gabbard (who, yes, is technically still in the race) and second choice was Sanders, for example, could see their vote move to Sanders if Gabbard is eliminated. (FairVote, a nonpartisan electoral reform group, advocates in favor of a ranked-choice system, which is currently used in Maine and other localities.)

The polls, fielded on February 25 and 26 by SurveyUSA and FairVote, asked 825 likely Democratic primary voters to pick their first choice for the nominee and rank the others in the field as their second through seventh choices. The margin of error for the poll ranged from 3.6 percent to 4.8 percent, changing slightly based on the number of people who answered the first question and the number who participated in the rankings. The survey was aimed at capturing voter preferences right after the South Carolina debate earlier this week.

In the standard poll, when voters were asked to choose their top choice, Sanders won with 28 percent of the vote and Biden and former New York City Mayor Mike Bloomberg both came in at 21 percent.

In the ranked-choice poll, when people were asked to rank up to eight candidates from their most to least preferred, and these picks were tallied using the same method that’s applied in ranked-choice voting, Sanders garnered 51.3 percent of the vote and Biden received 48.7 percent.

The ranked-choice result is closer than the standard poll — and within the margin of error — indicating that both candidates are popular choices among those who back other candidates.

The outcome of this poll differs notably from a national survey conducted last September when Sen. Elizabeth Warren beat Biden in a ranked-choice poll. At the time, Warren edged out Biden 53 percent to 47 percent, and Sanders came in third. The February survey indicates how voters’ support has shifted.

Walking through the results

Ranked-choice voting, a reform that’s gaining more support every election cycle, is ultimately aimed at ensuring that a broad spectrum of voter voices are considered. By factoring in voters’ second, third, and fourth choices, for example, the final result reflects the preferences of a wider swath of voters — so votes for candidates who don’t end up doing well in a crowded field aren’t entirely “wasted.”

Ranked-choice has been adopted by 20 cities and was first used by Maine for its statewide and federal elections in 2018. New York City also recently voted to begin using ranked-choice voting in local primary and special elections starting in 2021.

Voting this way can mean that voters will be nudged into getting to know more candidates, and candidates, too, could be pushed into campaigning across broader constituencies (rather than just trying to win enough for a plurality victory).

Ranked-choice voting can have positive effects on diversifying representation as well. Studies have found that a ranked-choice system increases the number of minority and women candidates who vie for elected office, partly because ranked-choice campaigning is less negative (candidates have incentives not to alienate someone else’s voters who could pick them as a second or third choice).

In this particular survey, this is how the ranked-choice results were calculated (these numbers don’t include undecided voters, who were factored into the data of the standard poll.)

Sanders started off with 29.6 percent of voters picking him as their first choice, while Biden and Mike Bloomberg were about tied for second with 22 percent each, former South Bend, Indiana, Mayor Pete Buttigieg and Elizabeth Warren got about 9 percent each, and Sen. Amy Klobuchar, billionaire activist Tom Steyer, and Hawaii representative Tulsi Gabbard were below that.

So Gabbard, Klobuchar, and Steyer’s votes are all redistributed. That doesn’t make much of a difference: Sanders then has 30.9 percent, Bloomberg and Biden remain tied with around 24 percent each, Buttigieg has 11 percent, and Warren has 10 percent.

Once Warren and then Buttigieg’s votes are redistributed, there’s a three-way race: Sanders has a solid lead with 41 percent, Biden is now in second with 31 percent, and Bloomberg falls to third with 27 percent.

Finally, Bloomberg’s votes are redistributed — and many more of his voters go to Biden than to Sanders. While Sanders remains in the lead in the end, it gets a whole lot closer — 51.3 percent to 48.7 percent.

When the polling is broken down across different demographic groups, Sanders maintains a strong lead in nearly all of them — though Biden keeps the lead among African American voters, and he and Bloomberg fare better than Sanders with voters over age 50.

In order to check out how the polling outcomes change when different candidates are removed, you can use an interactive tool on FairVote’s website.

As Vox’s Andrew Prokop has explained, it’s important to note that these results are weighted to be representative of a larger electorate:

The actual counts of voters are rounded from a weighted sample — they’re being presented here to help simulate how the tally would work in a real election, based on these poll results.

If ranked-choice voting was actually used in the Democratic nomination contest, it would likely have to be executed differently than in this poll, though — because of Democrats’ proportional delegate allocation rule.

The DNC requires that all candidates getting at least 15 percent of the vote be eligible for delegates. So theoretically, the ranked-choice method could be used to redistribute votes up to the point where there are only candidates with 15 percent or more remaining. In this case, the redistribution would end when only Sanders, Biden, and Bloomberg are left.

Finally, another interesting takeaway from the survey is just how popular ranked-choice voting is: 64 percent of the likely Democratic primary voters said they would support the use of ranked-choice voting in presidential primaries.