Biden doubters also hail disproportionately from swing states or districts. Thirteen out of 37 represent places that Biden lost in 2020 or won by fewer than 10 percentage points. This makes sense when you think about it: The reelection of representatives like Rep. Susan Wild could hinge on how well the Democratic presidential nominee does in their districts, and they may fear that Biden will drag them down with him if he loses big.
... yes, that's kind of why we're worried.
To be sure, it would be a political crisis for Biden to have even one elected Democrat saying he should drop out, let alone 10.