The feeling out here is that Feinstein no longer represents the largely progressive views of California. She's been getting attacked from the left often. There was a primary challenge from the left last time she was up for election, but it was a weak effort. She's so thoroughly entrenched that it's hard to remove her, even when many people in the state no longer feel she represents California Democrats well. But on the other hand she's usually more in line with people in social issues, so she has some cover. Still, I wouldn't be surprised to see her get challenged again (and perhaps more competently this time) if she does decide to run for another term.
EDIT: Also, it's hard for progressives in California to attack a feminist trailblazer like Feinstein. Even when she votes like this, people give her leeway.
