First Read is a morning briefing from Meet the Press and the NBC Political Unit on the day's most important political stories and why they matter.

Why Hillary Clinton needs to win California next week

Yes, Hillary Clinton is just 72 delegates away from crossing the 2,383 magic number needed for a majority of delegates to win the Democratic convention. Yes, she’s likely to hit that milestone before polls even close in California (due to the New Jersey primary and its 126 pledged delegates). And, yes, even if she loses in California by 10 points, her lead over Bernie Sanders in pledged delegates would still be twice the size of Obama’s lead over Clinton in 2008.

But here’s the reason why Clinton needs to beat Sanders in California next week: She doesn’t want to give him any legitimate rationale to remain in the race beyond June 7 or June 14 (the final primary in DC). Why? Because as our colleague Dante Chinni writes, the moment Sanders exits the race, her poll numbers against Trump will increase. “[T]o get a better look at where the Clinton-Trump race might stand after the nominating dust has settled, we recalculated the latest NBC/WSJ poll with Clinton capturing 70 percent of the Sanders-only vote. The result: those Sanders-only voters are worth an extra five points to Clinton. In the NBC/WSJ poll, Clinton's advantage over Trump goes from three points to eight points and she leads 51 percent to 43 percent.”

Maybe that’s why Clinton has canceled an event in New Jersey this week to spend more time in California, as NBC’s Kristen Welker reported on “Today” this morning.

Even as Sanders continues to move the goal posts

Then again, one thing that Sanders has successfully done over the past month is move the goal posts while trailing Clinton by 270 pledged delegates and more than 700 overall delegates. Here was Sanders before New York’s primary, which he lost by 16 points: “We will win a major victory here in New York next Tuesday.” And here he was before the Pennsylvania primary, which he lost by 12 points: "You know what? I think we're going to win here in Pennsylvania next week." And here was Sanders on “Meet the Press” last Sunday: “I think we have a good chance to win in California, maybe win big, and maybe win four or five of the other states that are off on June 7th… California is the big enchilada, so to speak.”

Given these past statements, even if Sanders loses in California, it’s possible to see him continue his campaign. But a loss in the Golden State would leave him without any legitimate rationale to flip superdelegates, especially when he trails in pledged delegates and the popular vote. And Sanders even acknowledged that reality on “Meet”: “Obviously, if we don't do well in California, it will make our path much, much harder. No question about it,” he said. The current Democratic delegate math:

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In pledged delegates, Clinton currently holds a lead of 270 delegates

Clinton 1,770 (54%)

Sanders 1,500 (46%)

Clinton must win 33% of remaining pledged delegates to get a majority in pledged delegates

Sanders must win 67% of remaining pledged delegates to get a majority in pledged delegates

In overall delegates (pledged + super), Clinton holds an overall lead of 769 delegates

Clinton must win 8% of remaining delegates to reach 2,383 magic number

Sanders must win 92% of remaining delegates to reach 2,383 magic number

Do Trump’s fundraising numbers for veterans add up?

As NBC’s Hallie Jackson reported on “Today” this morning, Donald Trump will hold a news conference at 11:00 am ET to respond to criticism that his January 28 fundraiser for veterans didn’t raise as much money as claimed. The Washington Post with more: “Last week — after intense pressure from the news media — Donald Trump made good on a promise he had made in January. He gave $1 million of his own money to a charity for veterans... On Tuesday morning, the day after Memorial Day, the presumptive Republican presidential nominee has scheduled a news conference at Trump Tower in New York. He is expected to announce that he had made good on a separate promise to veterans, made at the same time as the $1 million pledge... In January, on the night of the fundraiser, Trump was (seemingly) clear about the night's total haul. "We just cracked $6 million, right? Six million."

But that figure appears to be false. Earlier this month, Trump campaign manager Corey Lewandowski said the fundraiser had actually netted $4.5 million, because some big donors had not paid up. Then, a few days later, Trump said Lewandowski's figures were wrong. In fact, Trump said, the total fundraising haul was $5.5 million, after he had made good on his own pledge to give $1 million from his pocket.” The Clinton campaign will hold a conference call at 1:00 pm ET “to call out Donald Trump’s hypocrisy by fraudulently touting his support for veterans when his actual record has been one of disrespect,” per a press release.

Forget the dream third-party challenge to Trump and focus on the real third-party challenge -- Gary Johnson

For all of the media attention on whether a prominent Republican will mount a third-party challenge to Trump, here’s the reality: We already have a third-party challenge: former New Mexico Gov. Gary Johnson. And unlike a Mitt Romney/Ben Sasse/Paul Ryan running -- which is UNLIKELY to happen -- Johnson will have ballot access. MSNBC’s Jane Timm: “The Libertarian Party nominated former New Mexico Gov. Gary Johnson and former Massachusetts Gov. William Weld as its presidential ticket Sunday, as the party attempts to elevate itself into the mainstream during an election that's given the small party unprecedented opportunity.”

NBC|SurveyMonkey poll: Clinton leads Trump by 2 points

Finally, our weekly online NBC|SurveyMonkey tracking poll has Hillary Clinton leading Donald Trump by 2 points, 47%-45% -- down from 4 points last week (47%-43%).

On the trail

Donald Trump holds his press conference in New York at 11:00 am ET… And Bernie Sanders campaigns in California, hitting Emeryville, Santa Cruz, and Monterey. Don’t forget to check out the political unit’s rolling minute-to-minute coverage of all the latest 2016 developments at the On the Trail liveblog at NBCNews.com.