WASHINGTON — The only number that really matters in the Republican presidential race is 1,237 — that's the amount of delegates it will take to win the party's nomination.
In statistical terms the only thing being decided this week as a half-dozen states vote on Super Tuesday is how close Donald Trump gets to the halfway mark of that desired destination.
His opponents are desperate to limit Tuesday's damage lest it trigger a less tangible, more virtual reality: a sense that he's unstoppable, prompting a mass-stampede of people following the governors of New Jersey and Maine, and now a first senator, who've just hopped aboard the Trump Express.
Opponents are attacking him more viciously, and are already launching a pre-emptive message that whatever happens Tuesday is just another stop in a long, slow chug toward the final station.
"Here's the bottom line: You need 1,237 delegates to be the Republican nominee," Sen. Marco Rubio told Fox News Sunday. "Donald Trump will never have that number of delegates. I don't care how long I have to work -- I'll go to every state and territory."
In pure mathematical terms, Trump currently has only 81 delegates. Another 624 will be awarded Tuesday. He won't get anywhere near 624 because almost all these early states award delegates proportionally, so the poll-leading Trump is only likely to get a few hundred of them.
That still leaves two-thirds of the race ahead as the calendar shifts to winner-take-all states on March 15, with the most valuable contest of all in April: California and its 172 delegates.
Should Trump struggle in the later races against a narrower field, and fail to reach that magic number, the fight will shift to a nasty and potentially multi-ballot contest on the floor of the summer Republican convention.
One of the most respected political analysts in Washington remains a Trump-skeptic -- he admits his certainty is starting to waver after three straight wins by the improbable frontrunner, but he still doubts his ability to get to 1,237.
"Expectations (and momentum) don't matter. It's delegates," Charlie Cook told Meet the Press.
"I've been very skeptical about Trump winning the nomination from the very beginning. My knees are weakening a little. (But) when two out of three Republican voters... are against him, are they going to coalesce around him?"
But the Republican party is nervous.
Some of its more powerful figures warn that their party is sleepwalking into a general-election massacre. Their Senate leadership is reportedly preparing to run anti-Trump ads against their own party's candidate in the general election -- to spare electorally vulnerable lawmakers in swing states from being associated with him. The sense of incredulity is captured this week in a one-word headline on the front of the Economist with Trump drawn as Uncle Sam: "Really?"
The attacks on Trump have gotten far more vicious.
On Sunday alone, his well-documented real-estate dealings with members of the Italian Mafia were raised by Sen. Ted Cruz. He was asked about retweeting a quote attributed to the fascist Benito Mussolini. He was pressed on why he's being supported by the likes of former Ku Klux Klan Grand Wizard David Duke.
And he appeared to fumble the easiest question in American politics: Do you disavow the support of a Ku Klux Klansman? The no-brainer was rendered even easier by the fact that he'd already disavowed him in an earlier media scrum.
But when given the opportunity to answer the question three times on Sunday by CNN, he offered a shoulder-shrugging response: "I know nothing about David Duke. I know nothing about white supremacists."
As for the Italian dictator, Trump told NBC: "Mussolini was Mussolini. It's a very good quote... What difference does it make -- if it's Mussolini or someone else?"
The quote he recycled from a Twitter follower citing Mussolini was: "It is better to live one day as a lion than 100 years as a sheep."
It may as well have been a metaphor for the 2016 U.S. election. Because Republican brass are now frantically warning that the sheep are being led to the slaughterhouse.
"A first-rate con artist is on the verge of taking over the party of Lincoln and Reagan," Rubio said. He accused Democrats and the media of going easy on Trump now -- because, he said, they know he's unelectable in November and would instantly unleash what he called "the hounds of hell" the moment he won the nomination.
"If he's our nominee it could be the end of the Republican Party," said Rubio, who denounced Trump's handling of the KKK endorsement.
"It will split us and splinter us in a way that we may never be able to recover. And the Democrats will be joyful about it. It's not going to happen."
A roundup of general election polls at RealClearPolitics.com suggests Rubio would beat Hillary Clinton by five percentage points in a hypothetical general-election matchup -- the best score of any Republican.
That same site shows her beating Trump by three percentage points.
But the train kept chugging Sunday. As prominent members of the Republican party reacted with disbelief or disgust over the KKK exchange, Trump picked up an endorsement from his first U.S. senator.
Immigration hawk Jeff Sessions had been courted aggressively by his colleague Ted Cruz -- but there he was Sunday at a Trump rally, punctuating his endorsement by pulling on a red baseball cap embroidered with the slogan, "Make America Great Again."