this article about chucky schumer preparing to lead based on warren's wing is interesting. the real revealing paragraph for me was this one though, and i'm emphasizing what matters:
Schumer’s predecessor, outgoing Democratic leader Harry Reid (Nev.), did his best both in the majority and the minority to protect vulnerable incumbents such as Mary Landrieu (Louisiana) and Mark Begich (Alaska), using parliamentary tactics to avoid tough votes. But a byproduct of this was that Democrats didn’t articulate a clear agenda — and Landrieu and Begich lost anyway.
there's more good stuff. the rest is all here: