This being the 72nd anniversary of D-Day, I thought some military metaphors might best describe the California primary that will be held tomorrow.

Simply put, the California primary is Bernie Sanders's last stand.  If he loses, there is no reason that will be accepted by Democrats for him to continue with his campaign.  The calls for him to withdraw will be universal.

As for Hillary Clinton, she must win to convince skeptical Democrats that she has what it takes to win in November. 

The impact of a Sanders victory would reverberate across the country and might even change the dynamic of the convention.

Politico:

By winning the most delegates on the final day of the primaries (not counting the June 14 District of Columbia primary), Sanders would feel emboldened to defy the calls from establishment Dems to drop out. He would be more inclined to follow through on his pledge to contest the nomination at the convention. He would likely fight harder and concede less regarding the platform and presidential nomination rules. And because he would have close to a majority of pledged delegates (he already has 46 percent), he would be tempted to take more disputes to the convention floor in hopes of winning battles outright instead of settling for watered down language.

All of the above would make for, in Sanders’ words, a “messy” convention, not the stage-managed show of unity to which we’ve become accustomed. That could make for an even messier general election than we already expect. And a much weaker Hillary Clinton.

The Clinton campaign is already spinning a loss as no big deal.

Washington Times:

The Clinton campaign on Sunday expressed confidence heading into California, where the former first lady won in 2008 over Barack Obama. But the campaign is also downplaying the contest and stressing that Mrs. Clinton already is the Democratic Party’s presumptive nominee despite a tougher-than-expected challenge from Sen. Bernard Sanders.

“Well, I think if you look at the popular vote, if you look at the majority of pledged delegates, I should have captured those by Tuesday, but I’m going to keep fighting hard here in California and in the other states that are voting on Tuesday because I want to get as strong a vote as I possibly can,” Mrs. Clinton said during an interview on ABC’s “This Week” program. “But I think given where we are in this race, that I will have not only more than a 3 million-vote margin, but I will have a significant majority of pledged delegates by the close of voting on Tuesday.”

But this is whistling past the graveyard – especially since the latest polls show the race coming down to the wire:

For now, several late polls have pegged California to be a two-point race, including the widely respected Field poll, though others like the Los Angeles Times poll give Clinton a double-digit lead. Pollsters may be underestimating the Sanders vote, since nearly 2 million Californians have joined the voter rolls since January, mostly voters who are eligible to vote in the Democratic primary. And nearly two-thirds of them are under the age of 35, the Sanders sweet spot.

Much of the primary has settled along predictable lines. Sanders has won nearly of the activist-heavy caucus states, while Clinton cleans up partisan-heavy closed primary states. Sanders commands the youth vote and the independent vote, but Clinton’s big spread with older voters and moderates has made the difference in key states. While Clinton has been able to encroach on his turf – picking off liberal Massachusetts and blue-collar Ohio – Sanders has yet to turn the tables. California finally presents with him an opportunity to break from the script.

Even if Clinton loses California, she will still, almost certainly, be the nominee.  But precious weeks will pass with the Democratic Party still divided and Donald Trump turning to the general election.  There will be barely four months between the Philadelphia convention and election day – four months for Clinton to unify the party, raise half a billion dollars, and build a nationwide campaign. 

In short, a Sanders win will threaten her chances to win in November.  A Clinton win ends Sanders's campaign.  High stakes in a high-profile race.