Former state Senator Josh Newman (D), who was kicked out in a recall in June 2018 with 58% against, will run for the seat in the 2020 election, presumably against Senator Ling Ling Chang (R), who was selected as Newman's replacement in the recall. This will be the third go-round for the two, as Newman beat Chang in 2016 by 2498 votes. (Chang did not technically run against Newman in the recall -- the vote was an up or down against Newman, with Chang selected in a same day replacement vote).
The recall was launched over a gas tax and the Republicans push to deprive Democrats of a 2/3rds supermajority in the Senate. The Democrats quickly recapture the supermajority in the fall elections.