On Monday, longtime Democratic Sen. Dianne Feinstein confirmed what had long appeared likely: She will seek another term after 25 years representing the California in the Senate. The former San Francisco mayor became the state’s first woman senator following a 1992 special election, and she has easily won re-election ever since her last close call during the 1994 Republican midterm wave. However, at 84-years-old, there had been ample speculation that Feinstein would ultimately call it quits this cycle, but she dashed those suspicions with her recent announcement.
Although Feinstein hasn't had to seriously worry about a Republican opponent in a quarter-century, an intra-party challenge from Democrats may be in the works. The incumbent is relatively within the party's mainstream at the national level, but she is a relative centrist compared to California's more progressive Democrats. That's particularly so on national security issues and foreign policy during her service as the the top-ranking Democrat on the Senate's Intelligence and Judiciary committees at various times, while she recently voiced skepticism about single-payer health care proposals earlier this year.
As a consequence of Feinstein's relative moderation in this staunchly progressive state, there have been signs of possible campaigns from a few California Democrats who may oppose Feinstein from the left. State Senate President Kevin de León previously refused to rule out running in early September, and he'll be looking for a new gig anyway thanks to term limits forcing him out of his current office after 2018. Jonathan Martin at The New York Times reports that an unnamed party insider tells him that De Leon was set to “imminently” join the race and that Feinstein wanted to get ahead of his announcement with her own.
Wealthy financial entrepreneur Joseph Sanberg, who is active and well-connected in progressive political circles, has also taken steps that could portend a statewide campaign after he hired consultants and launched a new website. However, Sanberg has yet to publicly address whether he's interested in a campaign.
California's unusual top-two primary system also gives a relatively centrist incumbent like Feinstein a huge leg up over opposition from both the left and the right. All candidates run on a single primary ballot, and the top-two finishers advance to the general election regardless of their party affiliation. A progressive Democratic challenger would likely have to edge out any Republican candidates to face Feinstein, which is no small task unless there's a split field of multiple GOP candidates and only a single progressive challenger.
Even if a more progressive Democrat makes it to the general election against Feinstein, the incumbent may be able to to count on the support of Republicans and centrist voters if they view her as the more centrist option. However, that's not guaranteed, since there's evidence that a same-party general election causes participation to plummet among voters who backed the party that got shut out in the primary. Even when there was an all-Democratic general election in 2016’s open Senate race, Rep. Loretta Sanchez's attempts to reach out to GOP voters fell flat as she lost to now-Sen. Kamala Harris in a 62-38 landslide.
Nevertheless, it isn't even clear that Feinstein has lost the support of many progressive Democrats, and it may take a lot to convince them that it's time for change in this incredibly expensive state. Indeed, Harris immediately reiterated her support for Feinstein, and many other prominent California Democratic officeholders will likely join suit.