The Democratic race may already be over by the time the California polls open. According to The Associated Press, Hillary Clinton has already earned the 2,383 delegates needed to win the nomination. Yet in some ways California is still the most interesting contest between her and Bernie Sanders so far.

It’s hard to know how much the news may depress turnout, but it has easily been the closest contest in a big state, at least in the pre-election polls. And even though the election result won’t affect the outcome of the race, the stakes are nonetheless real: the chance for Mr. Sanders to continue making his case to change the minds of superdelegates heading into the convention.

High-quality polling provides a big picture

Mrs. Clinton leads Mr. Sanders in all the polls. But the polls are close enough that he could win.

On average, she leads by six percentage points among the six surveys that have been conducted over the last month. Four of them show an extremely tight race, with Mrs. Clinton leading by two points. The other two show her with a double-digit lead among likely voters.

It’s worth noting that we have the benefit of two of the most reliable polls in the business: the Field Poll and the Los Angeles Times/U.S.C./GQR poll. They show Mrs. Clinton with a two- and a 10-point lead, respectively. The P.P.I.C. poll, which has her up by two points, is also very well regarded.