We will call June 3 election day in California, but it's more accurately the final day of election month, and it promises to be a particularly lackluster one.

Voting by mail has become so pervasive in the state that roughly two-thirds of the ballots will have been delivered by the Postal Service. And the universal belief among political handicappers is that voter turnout may hit a new low.

Although voter registration has been rising as a proportion of Californians who are eligible to vote -- over the age of 18 and citizens -- actual voting by registrants has been drifting downward for years. This year's primary is a perfect storm of depressed voting.

It's a non-presidential primary, and it lacks an array of spirited duels that would draw voter interest. There's no U.S. Senate race this year. The state's dominant Democrats have, at most, pedestrian contests for statewide office -- with none for governor. There are no hot ballot-measure campaigns.

Some structural changes have contributed to that ennui. For instance, Gov. Jerry Brown and the Legislature decreed -- for expedient political reasons -- that initiative measures can go on only the November ballot, so the primary has only two measures, both placed by the Legislature, that lack sizzle.

Moreover, the advent of the top-two primary system for statewide, legislative and congressional offices more or less postpones the big showdowns until November.

How low could voter turnout go?

The last comparable primary election was in June 2010. But that featured some high-dollar battles for the Republican nomination for governor and an array of significant ballot measures. Even so, just a third of registered voters and fewer than a quarter of eligible voters cast ballots that year.

It's likely that this election's turnout will be even lower, perhaps 20 percent of eligible voters and scarcely a quarter of registrants.

Low turnout, coupled with increased voting by mail and the top-two system, changes the dynamics of the few genuine contests.

Having all candidates listed on the same ballot, with the top two facing each other in November, means that hopefuls angle to make it into the runoff, targeting the relatively few voters it takes to qualify. And that targeting cannot be confined to one's own party -- especially since low turnout likely translates into very low turnout of Democrats.

Moreover, targeting cannot wait for the last week, which has traditionally been when undecided voters make up their minds. With so many ballots being cast by mail, waiting until the last minute is a recipe for failure.

This election, like all elections, will have winners and losers. But with a relatively tiny number of votes being cast, and cross-party voting now the rule, finding any larger meaning in outcomes will be folly.