Sen. Kirsten Gillibrand has dropped out. Here are the 3 big winners.

• Sen. Kirsten Gillibrand has exited the 2020 presidential primary.
• Her supporters tended to be looking at lots of different candidates, making it hard for her to find a lane.
• Her exit specifically will help fellow Sens. Elizabeth Warren and Kamala Harris, as their constituencies tended to overlap.
• Sen. Cory Booker may also stand to gain, as he suffers from a similar issue as Gillibrand - and her exit makes it easier for him to overcome.

Sen. Kirsten Gillibrand has decided to exit the race for the presidency, and for the first time this cycle a candidate's exit could have a serious effect on the dynamics of the race.

While Gillibrand struggled to carve out a consistent percentage of the electorate who placed her as their first choice - the information that most pollsters tend to ask about in their horse-race polling - she was more popular than those numbers let on, based on INSIDER's polling.

We conduct a recurring SurveyMonkey Audience poll of Americans, each week or so asking more than 1,000 respondents about the candidates that they'd be satisfied with as nominee. We concentrate on the responses of people who say they're registered to vote and will likely participate in the primary process.

This allows us the unique perspective of figuring out the overlaps and the intra-party rivalries that are forming at this phase in the race. When a candidate exits, that helps their friends, not their ideological rivals.

And based on our data, Gillibrand's departure has the most potential upside for Sen. Elizabeth Warren and Sen. Kamala Harris.

Gillibrand dropped out at a smart time.

First, the stark reality of the senator's situation.

Though considered a compelling candidate early in the race - in the first five of our surveys, which ran from late December to late February, an average of 26% of people familiar with Gillibrand would be satisfied with her as nominee - that number slipped as peers such as Warren and Harris surged.

By comparison in the five most recent polls, running from early July to mid August, just 19% of those who knew of her would be satisfied if she were the nominee.

Though polling at this stage in the race is preliminary at best, candidates who want to be president ideally prefer such figures go up, not down.

Gillibrand was well-liked, but her supporters liked lots of people.

Looking at the polls since mid-May, the average Gillibrand supporter responded to our survey with 8 candidates that they would be satisfied with as nominee. That means that the average Gillibrand supporter was weighing seven other people, which leads me to believe that she was having issues sealing the deal with constituents. Only 3% of those satisfied with her listed her as the sole candidate they'd be satisfied with, and only 7 percent of her fans had it between her and one or two rivals.

In that same batch of polls, just 10% of Democratic respondents thought Gillibrand would beat President Trump in a general election. The generic response among Democrats is around 28%,

All this is to say that Gillibrand realized she wasn't breaking through and savvily quit while she was ahead.

Warren is the most obvious beneficiary.

Since May, there were 429 respondents out of 2,078 respondents who knew of Gillibrand, were registered to vote and said they'd participate in the Democratic primary. We can look at their preferences to get a sense of where they'll go.

• Overall, Warren is considered a satisfactory nominee by 56% of Democratic respondents who knew of her. That's really good, and just behind former Vice President Joe Biden.
• By comparison, Gillibrand's satisfaction rating among those who know her was just 21%
• However, 80% of Gillibrand fans would be satisfied with Warren as nominee.
• That's 24 percentage points higher than Warren's performance among general Democrats. That's enormous.

Other frontrunners such as Sen. Bernie Sanders and Biden also do better among Gillibrand fans, but it's by a fraction of the boost seen by Warren.

About two-thirds of Gillibrand fans would be satisfied with Biden as nominee. About three-in-five would be satisfied with Sanders. There are two other candidates that ridiculously outperform their numbers among Gillibrand supporters.

Harris has an opportunity as well.

78% of Gillibrand supporters like her West Coast counterpart, Harris.

That's well above the 54% satisfaction rating among Democrats who know Harris, and also 24 percentage points higher among Gillibrand fans.

While Harris hasn't enjoyed the same degree of polling support that Warren has, this exact moment - an ideologically similar colleague exiting the race - presents an incredible opportunity for Harris should she capitalize.

Sen. Cory Booker has an opening.

The Democrat from New Jersey, a longtime Gillibrand ally in the Senate, may have an inside track as well. Booker suffers from many of the same problems as Gillibrand. Though he's well liked, his supporters tend to be fans of several different candidates.

On average, those satisfied with Warren were satisfied with 4.1 other contenders, those satisfied with Harris as nominee liked 4.6 other candidates, but fans of Booker on average mentioned 5.7 other candidates as amenable nominees.

A disproportionate percentage (30%) of Booker supporters liked Gillibrand, so that number should actually drop as a direct result of Gillibrand's exit from the race, reducing the average number of rivals mentioned as satisfactory from 5.7 other candidates to 5.2, which is progress. Harris and Warren see a drop half as large.

And Booker can also capitalize on the fact that he's the single most disproportionately liked person among Gillibrand's fans: his satisfaction rate among Gillibrand supporters is nearly double his overall performance, a 28 percentage point jump from 37% of Democrats to 67% of Gillibrand supporters.

Harris and Warren have had steady rises, but Booker needs a solid win. Taking the PATH train from Newark to New York and pursuing some support could be the shot in the arm he needs.

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