WHERE WE ARE RIGHT NOW: Today is The Day of the Angst-Ridden Memos About Trump, as we enter the Frantic Scramble for the Off-Switch portion of the campaign.

Trump in Vegas (feeling lucky?) (Photo by Ethan Miller/Getty Images)

Heading into tonight's Nevada vote, Donald Trump is on course to win the 1,237 delegates he needs to be the GOP nominee. Chris Cillizza did the #Math, and says "the cake is very, very close to being baked for Trump... Something cataclysmic is going to have to happen — and soon — to keep Trump from being over or very close to the 1,237 delegates he needs to be the party's nominee when these primaries end on June 7."

The latest memo from the anti-Trump Our Principles PAC argues there's still time to stop Trump before he leads the GOP to "general election ruin in November."  

"Many have asked me, 'What can be done to stop Trump?'" writes executive director Katie Packer Gage. "The answer is simple: TRY.

"That’s right. No one has stopped him because no one has really tried." 

The memo laid out strategies for taking on the front-runner, and then their own #Math: March will feature 14 states that feature closed primaries, representing 597 delegates, they say: "As we saw in Iowa, efforts like the one we describe above are more effective in GOP-only primaries."

It's unclear whether the surge in Republican party I.D. this year has been Donald Trump's doing (although it does rate a strong "maybe.") But it's worth noting that in the primary states that have voted so far, the same candidate has won registered Republicans both times: Donald Trump.

(And of course: Iowa wasn't actually a "primary." The relative strength of the Trump ground game may remain a mystery, but in general that factor tends to be more critical in caucus states -- a proposition for which the first Obama campaign serves as Exhibits A, B and C. And the overwhelming majority of delegates in March won't be delivered via caucus votes.)

Nevada. / AFP / JOSH EDELSONJOSH EDELSON/AFP/Getty Images

All this has some rival campaigns defining success down, apparently. Today, John Kasich's team highlighted the fact that in the new Quinnipiac poll that has him trailing Trump in Ohio, he appears to be losing his own home state to the front-runner by a lot less than Marco Rubio is losing his. (John Weaver in a memo to reporters: "Marco Rubio stock is the ultimate insider bubble.")

Ted Cruz is faring better on his home turf; he's winning Texas in the Texas Tribune poll out today. But that poll has his lead in the single digits, an edge that probably wouldn't allow him to stockpile the delegate haul he'd been counting on from that contest. After scoring no delegates in South Carolina, the Cook Political Report is estimating that Cruz has picked up just 17 percent of the delegates he should have from the states that have voted to date. That figure for Trump: 115 percent. 

(On a related note: Five months ago, the Post's Dana Milbank said he'd eat a column if Trump won the GOP nomination. Now he says he "may be soliciting recipes for wood pulp." If you know any, please do flag them for @milbank on Twitter.)

Trump does Vegas. (Photo by Jabin Botsford/The Washington Post)

IT'S ELECTION DAY: Republican caucuses in Nevada begin between 5 p.m. and 7 p.m. PT (8-10 p.m. on the East Coast.) They wrap at 9 p.m. PT/12 a.m. ET.

--You can get live results here tonight.

--You can find the only Twitter list you need to follow the Nevada caucuses here.

--And you'll find Post coverage of the vote here: As of this moment, the consensus seems to be the Nevada caucuses are Trump’s to lose — and he still could, reports Philip Rucker. Sure, he's had double-digit leads in recent polls. He's drawn massive crowds in the state. And his immigration message seems tailor-made to resonate with his conservative white, working class base in a state where the Latino population is booming. But Nevada's caucuses are "peculiar and unpredictable" -- and it's worth noting that they still seem to be working out a few kinks

(Rubio didn't stick around for the results -- earlier today, he left for stops in Minnesota and Michigan.)

BACK TO SOUTH CAROLINA:

Three more days until South Carolina Democrats weigh in. EPA/ERIK S. LESSER

Heading into Saturday's Democratic primary in South Carolina -- where Hillary Clinton the heavy faorite in large part because of her strength with black voters -- Dave Weigel notes the flip side of that equation: Her relative weakness with white ones. In other words: 2008, reversed. 

Today in South Carolina, Trayvon Martin's and Eric Garner's mothers campaigned with Hillary Clinton, and the Sanders campaign released a radio ad featuring Spike Lee. Speaking of big-name endorsements: Rep. Jim Clyburn is saying Bernie Sanders never even tried to get his.

Off the trail, a judge ordered discovery to go forward over Clinton's private email system. (U.S. District Judge Emmet G. Sullivan: “There has been a constant drip, drip, drip of declarations. When does it stop?”)

ON THE AIR: U.S. companies who offshore profits have long had a starring role in the Trump stump speech. Now they're featured in a new Clinton ad. (VIDEO)

The Sanders contrast push today included a knock on Clinton over NAFTA support. 

TRAIL MIX: A Koch brothers adviser joins the Rubio team.

--There are plenty of "dirty tricks" allegations against Ted Cruz. There hasn't been much proof to back them up.

-- Following racism allegations, the Cruz campaign pulled work from Sabo (the artist who was essentially Cruz's Shepard Fairey, except he made his candidate a "ripped, tattooed smoker"), the Texas Tribune reports.

-- Marco Rubio is skipping CPAC, and so far nobody can seem to agree on exactly how that happened, but they all seem pretty unhappy about it.

--The GOP field pushed back on Obama's Guantanamo plan, but it might not matter: The president may have waited too long to unveil it, says Amber Phillips

-- Ted Cruz hardens his stance on immigration: he now says he will find and deport undocumented immigrants -- a shift from last month.

-- Ben Carson said he's seen "what real racism is," while Obama was "raised white." 

THE BIG NUMBER: Air wars edition

MORE TRAIL MIX: VP SPECULATION TIME! Here are some early Trump veepstakes. And on the Democratic side, here's a look at Julián Castro, who could be VP next year, or out of a job. One of those things.

-- Donald Trump has now either done a 180 or a 360 on the Obamacare individual mandate.

-- Stuff Surrogates Say: Giuliani on Trump: “I never represented him, because he considers a legal bill the first offer in a negotiation." 

-- Glenn Beck's been brandishing what he says is George Washington’s copy of Don Quixote at Cruz rallies. Mount Vernon begs to differ.

-- The only Goldman Sachs employee to donate to Trump has also trademarked the phrase "Make Christianity Great Again."

WHEN METAPHORS COLLIDE:

THE VIEW FROM THE FIELD:

Last summer, Trump hats were an ironic accessory in Williamsburg and Silver Lake. Recently, it got a chillier Fashion Week reception.

#TBTuesday (it's not a thing, but that's never stopped us before):

Here's Donald Trump, reacting to a protester at a Nevada rally earlier today: "I love the old days, you know. You know what I hate? There's a guy totally disruptive, throwing punches -- we're not allowed to punch back anymore. You know what they used to do with guys like that in a place like this? He'd be carried out on a stretcher, folks..."

YOUR DAILY TRAIL PIT STOP: On that note: Here's supercut of presidential candidates telling hecklers to buzz off. (VIDEO)