Feinstein, the oldest member of the Senate, is widely respected by senators in both parties, but she has noticeably slowed in recent years. Interviews with more than a dozen Democratic senators and aides show widespread concern over whether the California Democrat is capable of leading the aggressive effort Democrats need against whoever President Donald Trump picks to replace the late Justice Ruth Bader Ginsburg…

Feinstein sometimes gets confused by reporters’ questions, or will offer different answers to the same question depending on where or when she’s asked. Her appearance is frail. And Feinstein’s genteel demeanor, which seems like it belongs to a bygone Senate era, can lead to trouble with an increasingly hard-line Democratic base uninterested in collegiality or bipartisan platitudes.

Just this week, Feinstein infuriated progressives after declaring her opposition to ending the Senate’s legislative filibuster — a top goal of party activists if Democrats win full control of the Congress and White House in November. Some on the left called on her to resign over the comments, although other Democratic moderates have expressed similar views.