Though only modestly discussed in the national media, California's primary election will figure heavily in the Democratic 2020 presidential nomination process. That's because California, normally an afterthought in presidential nominations with its June primary, has moved its contest to March 3rd. This could have a number of large effects on the early stages of the "visible" primary that year.
Perhaps most consequential is that California will be using early voting, starting around four weeks prior to the contest. That means, according to University of North Carolina–Wilmington political scientist Josh Putnam's primaries calendar, California Democrats will be able to participate in the presidential nominating contest right around the same time Iowa caucus-goers can, and a week before New Hampshirites weigh in. South Carolina's primary will be held only four days before California's polls close.
Chances are most or all of the presidential candidates will pay homage to Iowa and New Hampshire as the early taste-testers for the rest of the nation, and will thus campaign heavily in those early states. They'll likely do a substantial amount of campaigning in the other early states of Nevada and South Carolina. But they now can't afford to ignore California.
This is because California is huge. Roughly 11 percent of the Democratic National Convention's 2020 convention delegates will be sent by California. Those delegates will be selected proportionally, meaning the narrow winner of a crowded primary field is not going to clean up in that state. But the candidate who fares well in that state will be well on his or her way to the delegates needed for the nomination.
What effects will California's earlier primary have on the national election? There are several possible areas:
Campaigning in California is extremely pricey. It's a geographically vast state with some of the most expensive advertising markets in the country. And unlike New Hampshire and Iowa, it can't be won on retail politicking; you just can't shake hands with 8.5 million Democrats living along an 850-mile coastline. Candidates wishing to be competitive there will need to raise a lot of money very early. Doing unexpectedly well in Iowa won't be enough to boost coffers for California, since early voting will have already begun there. This will favor candidates who already have a very strong nationwide organization well before February.
Ideology & Issues
It won't surprise anyone to learn that California is quite liberal. Its active Democrats may be well to the left of those in Iowa and New Hampshire. They also likely care about a somewhat different set of issues than Democrats in more rural, whiter states do. Candidates campaigning in California will be pressed repeatedly on whether they support recreational marijuana legalization, whether they back California's carbon emission and electric vehicle goals, how many women and people of color they'll promise to hire into their cabinets or place on the Supreme Court, if they'll support municipal safe havens for undocumented immigrants, and so forth. Taking stances that California Democrats want to hear can be extremely valuable for securing donations, volunteers, and votes there, but could potentially jeopardize such support in other states, and would almost certainly be used against them by Republicans should they win the nomination.
Of the vast number of candidates currently in the running for the Democratic nomination, two major ones are from the Golden State: Los Angeles Mayor Eric Garcetti and Senator Kamala Harris. There's no guarantee that either of them will win the state's primary, of course. But if they're both still in the running a year from now that could set up a substantial northern-southern division in the primary field.
If only one of them remains in the race, that could complicate matters by possibly making the contest less relevant. Democratic candidates in 1992 largely blew off the Iowa Caucus since Iowa Senator Tom Harkin was running for president and was expected to dominate his home state's contest (which he did). Bill Clinton only came in second in New Hampshire that year, but because the winner, Paul Tsongas, was from neighboring Massachusetts and enjoyed huge name recognition in the Granite State, many political observers discounted Tsongas' win. If, say, Kamala Harris looked overwhelmingly likely to dominate the California primary, it's unlikely that other candidates would ignore the contest—there are too many delegates at stake—but a win by her wouldn't be seen as particularly special. It would be hard for her to beat expectations.
Political observers and reformers have been complaining about Iowa's and New Hampshire's dominance of the presidential nomination cycle for decades. California hasn't exactly dethroned those states, but it's substantially destabilized their dominance, and it will be a while until we know exactly what kind of effect that's had and whom it's benefited.