The strategic case for Elizabeth Warren’s candidacy has typically relied on two similar arguments. The first is that she is a “unity candidate” who can bring the left and right flanks of the Democratic Party together. The second, addressed to the Left, is that she can expand a supposed Sanders-Warren coalition without simply eating into the Sanders base by bringing in right-flank voters.

Neither of these arguments were ever particularly credible, but both have become much weaker. Over the past several months, Warren’s right-flank supporters have fled her camp while a disproportionate core of second-choice Sanders supporters have remained. Increasingly, her role in this race is holding on to that base and — as one Warren campaign staffer said Saturday night — “blunting the momentum for Bernie Sanders.”

To get a sense of what is going on with Warren’s coalition, I divided it into two groups: those who support Bernie Sanders as a second choice, and those who do not. Here’s how her second-choice support has changed since July: