One stat explains why Bernie Sanders had to spend the entire debate fending off low-polling rivals

BRENDAN SMIALOWSKI/AFP/Getty Images

Democratic debate in Detroit, Mich.

• We've been polling overlaps in support among the Democratic field.
• Candidates who have constituencies that also would be satisfied with Sen. Bernie Sanders as nominee include Andrew Yang, Rep. Tulsi Gabbard, Sen. Elizabeth Warren, Joe Biden, and Marianne Williamson. Only two were on stage.
• Candidates with bases that don't care for Sanders include Sen. Amy Klobuchar, Rep. Tim Ryan, Gov. John Hickenlooper, Rep. John Delaney, Rep. Beto O'Rourke, and Mayor Pete Buttigieg, all of whom were on stage.
• The requirements of the next debate are pushing candidates to establish a lane, and anti-Sanders seems to be an attractive one for a fair share of candidates.
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During the first night of the second batch of Democratic debates in Detroit, a fairly consistent routine would happen: Sen. Bernie Sanders would be pressed on a policy, then one of a number of rivals who had criticised that policy would respond, and the segment would descend into Sanders and perhaps fellow frontrunner Sen. Elizabeth Warren carrying on the dispute.

In part, this repetitive process was the result of CNN's strategy in framing questions, and it was in part due to the do-or-die requirements laid out by the Democratic National Committee in order to obtain a spot in the next set of primetime debates. But largely, it's due a unique attribute shared by most of the people participating in the first debate: who else their voting constituency would vote for.

INSIDER has been conducting a recurring series of national polls through SurveyMonkey Audience regarding the Democratic primary field since December. Most other horse race polling is concerned with who respondents would support were the election held today. Instead, we ask respondents to select all the candidates they would be satisfied with in the event they were the eventual nominee.

Read more: How the INSIDER 2020 Democratic primary tracker works

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Data as of early July.

Our approach isn't as instructive when it comes to the major contours of the race, but does give us a great angle as to which candidates are competing for overlapping groups of constituents. People only get one vote, and this lets us figure out which voters are discerning between a few candidates. Most relevant here, we also ask people which candidates they would be unsatisfied with, in the event they became nominee.

First, let's break candidates into five groups based the 11 polls we've run since April. We're going to look at the two top rivals of the candidates based on who their constituents most like, and for the sake of simplicity I'm only looking at candidates who have made a debate.

1. Candidates whose supporters most like Joe Biden and Kamala Harris: Sen Amy Klobuchar, Sen. Cory Booker, Rep. Tim Ryan, Gov. John Hickenlooper, and Rep. John Delaney.
2. Candidates whose supporters most like Elizabeth Warren and Joe Biden: Sen. Kamala Harris, Sen. Michael Bennet, Mayor Bill de Blasio, Gov. Steve Bullock, Rep. Beto O'Rourke, and Sen. Bernie Sanders.
3. Candidates whose supporters most like Elizabeth Warren and Kamala Harris: Secretary Julian Castro, Sen. Kirsten Gillibrand, Mayor Pete Buttigieg, Gov. Jay Inslee.
4. Candidates whose supporters most like Bernie Sanders and Elizabeth Warren: Marianne Williamson, Rep. Tulsi Gabbard, Andrew Yang, former Vice President Joe Biden.
5. Elizabeth Warren, the only candidate whose supporters most like Sanders and Biden.

For the candidates in night one, Sanders was the single most popular candidate listed by their backers as unsatisfactory as nominee.

Indeed, Sanders was listed as unsatisfactory by large chunks of the supports of all the people on stage tonight, with the exception of Elizabeth Warren.

Overall - of the 3,774 respondents polled over the period who had heard of Sanders and said they'd vote in the Democratic primary - just shy of a quarter are unsatisfied with him as nominee, about half would be satisfied with him as nominee, and another quarter aren't committed either way.

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Presidential candidate John Delaney.

The candidates on stage Tuesday - with the exception of Warren - are trying to consolidate support in the anti-Sanders lane. Concentrating only on serious contenders, 31% of Klobuchar backers, 22% of Ryan backers, 34% of Hickenlooper backers, 29% of Buttigieg fans, and 25% of O'Rourke backers would be unsatisfied with Sanders.

(Marianne Williamson and Steve Bullock have very low sample sizes based on their comparative obscurity, I'm going to set them aside for now. Of the 4,408 Democratic primary supporters polled over the period, only 56 were satisfied with Delaney, a level far too low to draw conclusions regarding how they feel about Sanders.)

None of these candidates pose a serious threat to Sanders at the moment. Only Warren is above water; everyone else in the field has considerably lower support among Sanders fans than they do among Democrats overall. Besides Warren, who had a detente with Sanders, the closest rival on stage among Sanders supporters was O'Rourke, who only 28% of Sanders fans like.

That's the dynamic that led to the odd alliances on the stage. Only one other person has a solid constancy that seriously likes Sanders, while everyone else sees little upside in targeting an overlap that doesn't exist and potential gains in cementing a reputation opposing one of the more salient leftists in the field.

The result may have been grueling for the pair at center stage, but it certainly reminded viewers why they were at the center of the stage.

Read More:

• How the INSIDER 2020 Democratic primary tracker works
• 2020 Democratic presidential primary power ranking