Who will run in Maryland's 3rd congressional district now that Democrat John Sarbanes is not running for re-election

A solidly Democratic district. 

Source:  Ballotpedia

Maryland Matters,  10/26/2023

Sarbanes had once been considered a potential future candidate for U.S. Senate, where his father, Paul Sarbanes once served. That seat is currently held by Sen. Ben Cardin (D), who is also not seeking re-election in 2024. 

But in recent reports, Sarbanes appeared to be winding down his fundraising efforts. He raised just $2,000 in the second quarter of this year. 

Since he was first elected in 2006 to succeed Cardin — who succeeded his father in the upper chamber — the younger Sarbanes has been a leading voice for campaign finance reform in Congress.

 

Wikipedia

So far, five Democrats and no Republicans have announced they are running to succeed Sarbanes.

Other dropouts:

Debbie Lesko, R, AZ-8.  (11/28/2023

Anna Eshoo.  D, CA-16.  (11/29/2023)

Tony Cardenas, D, CA-29.  (11/29/2023)

Grace Napolitano.  D, CA-31.  (11/29/2023)

Ken Buck, R,CO-4.  (1128//2023)

Victoria Spartz, R, IN-5.  )(11/28/2023)