Under state legislation signed by Gov. Jerry Brown, California will hold its 2020 presidential primary in March rather than early June, as it has been since 2008. Intended to increase the populace state's influence in the primary process, with this shift California will now contribute 37 percent of the elected delegates on Super Tuesday, a factor which will have broad implications for the 2020 election cycle.
In December of 2018, Democrat Sean Frame filed a statement of candidacy with the Federal Election Commission, announcing his intention to seek the CA CD 4 seat in 2020. On May 1, 2019, Brynne Kennedy filed her statement of candidacy announcing her run for Congress in CA CD 4. Brynne Kennedy is a tech entrepreneur, author, and resident of Roseville, CA.
A Democratic congressional candidate nearly won the district in 2008, losing by only half a percentage point and less than 1,600 votes, indicating that the district was much more competitive than it appeared to be. But in the more recent  2012 and 2014 elections the Republican candidate won over 60% of the vote indicating the District remains solidly Republican.
New district boundaries for the 2012 elections shifted the population center to the south and east. Registered Democrats and Independents/Decline to State voters in the new district area outnumber registered Republicans by 12%. However Republicans, Independents/Decline to State and small third parties outnumber Democrats well over a 2 to 1 ratio. There are 183,800 Republicans, 117,300 Democrats and 97,200 other.
While 2018 saw 7 of California's Republican held House seats fall to Democrats, Republican Tom McClintock held his district by more than 8% over centrist Democrat Jessica Morse.
In 2018, six Democratic candidates filed statements of candidacy with the Federal Election Commission (FEC). They were, in alphabetical order by last name: Regina Bateson; Roza Calderon; Richard Martin; Robert Lawton; Jessica Morse; and Rochelle Wilcox. Martin and Wilcox dropped out of the race, with Wilcox endorsing Morse in February.
Retired Air Force Lieutenant Colonel Charlie Brown, who was the Democratic nominee for this seat in 2006 and 2008, was "seriously considering" running in 2018, but decided in June 2017 against a third campaign. In January 2018, Brown endorsed Morse for the nomination. Bob Derlet, the Democratic nominee in 2016, also endorsed Morse in January.
On the Republican side, McClintock has one challenger, Mitchell Kendrick White, who filed with the FEC in January.
In February, the California Democratic Party endorsed Jessica Morse for the Democratic Nomination. However, the California jungle primary system means that only the two candidates with the most votes on June 5, regardless of party, will go on to the general election on November 6. Both Republicans and four Democrats appeared on the jungle primary ballot.
Morse won the Democratic Primary in June of 2018, but in November, McClintock held the district with an 8+ advantage in November.
In December of 2018, businessman and activist Sean Frame announced he would be a Democratic candidate in the 2020 race for California's 4th congressional district.
Living former Members
As of April 2015[update], there are two former members of the U.S. House of Representatives from California's 4th congressional district that are currently living.
^"Federal Election Commission, Registered Candidates in California's Fourth Congressional District". Federal Election Commission. Retrieved July 27, 2017.
^"Rochelle Wilcox". Rochelle Wilcox. Archived from the original on 2018-01-19. Retrieved 2018-01-25.
^@Morse4America https://twitter.com/Morse4America/status/969295288740470785. Archived from the original on 2018-05-07. Retrieved 2018-01-12. Missing or empty |title= (help)
^Johnson, Doug (April 8, 2017). "Although Tough on Trump, McClintock Faces Backlash at Another Town Hall". KTXL. Archived from the original on April 11, 2017. Retrieved April 10, 2017.
^"I am thrilled & grateful to be endorsed by Charlie Brown, 2006 & 2008 Congressional Candidate for #CA04. From Charlie: "Jessica has the knowledge & experience to best represent the people in the 4th Congressional District." To read his full statement:". Archived from the original on 2018-05-07.
^Morse, Jessica (January 11, 2018). "We are so grateful to have the support of community leaders, such as Dr. Bob Derlet - the 2016 Democratic candidate for #CA04! "I am behind Jessica because she is a fighter. She will stand up for the people of this district & not back down." Thank you, Dr. Derlet! #JessWeCanpic.twitter.com/e5tv0OC6bk". @Morse4America. Archived from the original on May 7, 2018. Retrieved 2018-01-12.
^"PAGE BY PAGE REPORT DISPLAY FOR 201801199090468752 (Page 1 of 1)". docquery.fec.gov. Retrieved 2018-01-25.
^ ab http://www.thepresstribune.com/article/2/27/18/jessica-morse-wins-contested-endorsement-california-democratic-party. Archived from the original on 2018-02-28. Retrieved 2018-02-27. Missing or empty |title= (help)
^"California's 4th Congressional District election, 2018". Ballotpedia. Retrieved 2019-03-03.
GovTrack.us: California's 4th congressional district
California Citizens Redistricting Commission: wedrawthelines.ca.gov 2012 final district maps