Sen. Dianne Feinstein (D-CA) (L) participates in a reenacted swearing-in with her husband Richard C. Blum and U.S. Vice President Joe Biden in the Old Senate Chamber at the U.S. Capitol January 3, 2013 in Washington, DC.Chip Somodevilla | Getty ImagesSen. Dianne Feinstein and her husband will be hosting former Vice President Joe Biden next month in San Francisco, according to an invitation obtained by CNBC.The emailed flyer shows that Feinstein, along with her husband Richard Blum, are co-hosting the event on Oct. 3. They will be joined by several other co-hosts including Denise Bauer, a former ambassador to Belgium. Feinstein had already committed to backing Biden’s candidacy for president before he announced his campaign in April. This would mark the first time she’s hosted a fundraiser for the former vice president in the 2020 election cycle. Her husband has taken part in various fundraising events for Biden.”My candidate would be Joe Biden,” she said in January. “I watched him as vice president. I’ve seen him operate. I’ve seen him perform and I think he brings a level of experience and seniority, which I think is really important.”Feinstein’s California colleague in the Senate, Kamala Harris, is also running for president and has memorably tangled with Biden on the debate stage.Tickets for the event start at $1,000 and go up to $2,800. The gathering will be same day as billionaire and real estate executive George Marcus is co-hosting a separate fundraiser in Northern California. He finished the second quarter raising $21.5 million and the Real Clear Politics polling average has him ahead of the primary field.A political spokesman for Feinstein confirmed she will be co-hosting the event. A spokesperson for Biden did not return a request for comment.The two have been close for years. When Feinstein ran for reelection in 2018, Biden attended one of her fundraisers. She eventually went on to win that race in a landslide.