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The contests, across 12 states and territories, herald several weeks of nationwide skirmishes

The sheer scale of the battlefield favors Donald Trump and Hillary Clinton

CNN  — 

Super Tuesday is likely to live up to its billing for Donald Trump.

The first day of multiple-state voting looms large in a wild presidential race after early states trimmed the field and the brash billionaire and his army of outsider voters are positioned to send panic through the Republican establishment by tightening his grip on the party’s nomination.

READ MORE: Donald Trump got endorsed by the KKK

Hillary Clinton – boosted by her huge win in South Carolina on Saturday – is meanwhile hoping to start locking out her Democratic rival Bernie Sanders, who is giving her a tougher-than-expected challenge, by showing the strength of the Southern foundation of minority voters on which her campaign is built.

Both Trump and Clinton head into the most important day yet in the 2016 election dominating their respective races. A CNN/ORC national poll out Monday shows Trump getting 49% of the Republican primary vote – 30 percentage points ahead of Florida Sen. Marco Rubio. On the Democratic side, Clinton tops Sanders 55% to 38%.

The billionaire is, however, struggling to shake off a controversy after he failed to disavow former Ku Klux Klan grand wizard David Duke during an interview on CNN’s “State of the Union” on Sunday. Trump blamed a bad earpiece for the oversight, and he has at other times disavowed Duke, but his rivals were quick to seize on the incident to suggest that he is unfit to be the Republican nominee.

Rubio said the remarks prove that the former reality show star is “unelectable.”

“I don’t care how bad the earpiece is, Ku Klux Klan comes through pretty clearly,” Rubio said during a rally in Tennessee Monday.

Fellow GOP opponent John Kasich also disavowed White supremacists on CNN Monday when asked about Trump’s response.

“I don’t know what’s in his head,” the Ohio governor told New Day’s Alisyn Camerota. “All I know is that white supremacist groups have no place in our society and clearly not in the Republican Party.”

Former presidential candidate Mitt Romney also chimed in on Monday.

“A disqualifying & disgusting response by @realDonaldTrump to the KKK. His coddling of repugnant bigotry is not in the character of America,” tweeted Romney, who has been actively hitting Trump for days.

READ MORE: Why Tuesday is still super

The contests on Tuesday, across 12 states, herald several weeks of nationwide skirmishes that will be decisive in determining who gets to face off for the White House in the fall.

The sheer scale of the battlefield favors Trump, whose ubiquitous media profile means he is known everywhere, and Clinton, whose decades in public life give her an advantage over the lesser-known Sanders.

Clinton looks to close Sanders out in March

It’s Trump who may stand tallest on Tuesday night.

“On Tuesday, you have a big day,” Trump told supporters at a big rally in Tennessee on Saturday, saying he didn’t care if someone was at death’s door or if their wife was leaving them – they had to vote.

“You get up, you go to the polls, and you vote!” he said. “I promise you, that you are going to look back on this night and you are going to say this was a very important night … a very important evening in your life.”

While Trump expects to savor a night of triumph, his top rivals, Rubio and Texas Sen. Ted Cruz, have lesser expectations. Rubio is desperate to at last secure an elusive win, somewhere, anywhere. And Cruz faces a make-or-break moment in his home state of Texas.

RELATED: Rubio on Trump: ‘He’s not gonna make America great, he’s gonna make America orange’

A total of 595 Republican delegates are up for grabs of the 1,237 needed to clinch the GOP nomination. Sanders and Clinton are facing off for 865 of the 2,383 delegates needed to win the Democratic race.

Nightcap: Trump stumbles into racially charged controversy over white supremacist supporters | Sign up

Republicans are competing for delegates to be awarded Tuesday in Alaska, Alabama, Arkansas, Georgia, Massachusetts, Minnesota, Oklahoma, Tennessee, Texas, Vermont and Virginia.

Democrats will award delegates in the same states as Republicans, apart from Alaska, and they are also competing in Colorado and in American Samoa.

A fateful moment

Super Tuesday is coming at a fateful moment in the Republican race. It has finally dawned on rival campaigns and party establishment figures that far from fading as many predicted, Trump – after his three thumping wins in New Hampshire, South Carolina and Nevada – will clinch the nomination unless there is a dramatic twist in the race.

That realization spurred bitter clashes between Trump and Rubio on Friday and over the weekend and has Cruz also gunning for the billionaire. And it played into former candidate Chris Christie’s endorsement of the erstwhile reality star he had once billed as unfit for the presidency.

Ted Cruz, worried about Super Tuesday, goes hunting for delegates

Republican leaders and operatives, meanwhile, are wondering whether the blitz against Trump by Rubio at CNN’s debate in Houston on Thursday came too late to halt the billionaire businessman.

“I am not sure throwing the whole kitchen sink is going to make much difference in the trajectory of the race,” said Ford O’Connell, a GOP strategist not currently working for any presidential candidate. “Political scientists are going to wonder for years why they didn’t go after him a lot earlier.”

WHO’S WHO REPUBLICANS: Who is John Kasich? | Who is Marco Rubio? | Who is Ted Cruz?

WHO’S WHO DEMOCRATS: Who is Hillary Clinton? | Who is Bernie Sanders?

Polling is sparse in some states, so it’s difficult to be certain about the outcome everywhere. But it’s possible that Trump could barnstorm to victories in as many as 10 contests and whip up an unstoppable tailwind.

His rivals are already bracing for a tough night.

“Nobody’s going to win but Trump.” Kasich, who is hoping to remain viable until the race turns north, told CNN’s Sara Murray on Thursday.

Cruz, a Texas senator, added on Friday: “Right now, Donald Trump has enormous momentum.”

He added, “If he continues with that momentum and powers through and wins everywhere on Super Tuesday, he could easily be unstoppable.”

Rubio is on a high after a stellar debate performance last week in which he pulled off the most effective prosecution yet of the Republican front-runner. But the euphoria could be dampened by the Super Tuesday math.

Despite the Republican establishment flocking to the Florida senator, seeing him as the strongest anti-Trump candidate, he has yet to win a single contest after four states held votes – and it is not obvious where that might happen on Tuesday.

His best chances appear to come in states that have a mix of religious, conservative and highly educated white-collar voters.

That’s why the Rubio campaign and his Super PAC, Conservative Solutions, have been buying television advertising in areas including the Washington media market that covers the populous Northern Virginia suburbs and the region around the state capital of Richmond, according to Federal Communications Commission records. Rubio spent the entire day in Virginia on Sunday.

Rubio supporters such as Wisconsin Rep. Sean Duffy are predicting he can win Minnesota as well.

“Wait ‘til Tuesday. As the field narrows, there is a consolidation of votes that I think are opposed to Donald Trump and those are going to go to Marco Rubio. We are going to see that consolidation, I think, project itself in wins,” Duffy said on CNN.

But even if he is left winless on Tuesday, Rubio can survive because his must-win home state primary in Florida is on March 15. In theory, he could lose all of the Super Tuesday contests and start to overtake Trump when states start doling out delegates on a winner-take-all basis in mid-March.

Make or break for Cruz

For Cruz, his win-or-go-home moment is now.

“If Cruz doesn’t win Texas, it is game over for him,” said Phillip Stutts, a Republican political consultant. “Rubio doesn’t have to win, but Cruz has to.”

Trump’s big advantage going into Super Tuesday is that his opposition remains divided.

Cruz, Rubio and Kasich in some states are dividing up the anti-Trump vote between them, meaning no single candidate can unite opposition to Trump.

“Right now, they are all fighting each other while Donald Trump wraps up delegates. That’s a problem – it needs to be a two-man race,” said Stutts.

For instance, in Virginia, Trump leads with 41% while Rubio is at 27%, Cruz is at 14% and both Kasich and former neurosurgeon Ben Carson have 7% each, according to a Monmouth University poll last week.

And in Massachusetts, it’s Kasich who is inadvertently helping Trump – sitting tied in a WBUR poll with Rubio at 19% – well behind Trump at 40%.

Find your presidential match with the 2016 Candidate Matchmaker

Even if Trump does sweep the field on Super Tuesday, his nomination will not be assured, however, because in the GOP, all states that vote before March 15 must divide delegates among the competing candidates based on their share of the vote, as long as they reach certain thresholds in some states.

But the real estate mogul could carve out a strong delegate lead ahead of big-state winner-take-all primaries such as Ohio and Florida in two weeks, where first-place finishes could effectively make him the Republican nominee.

Cruz, who once looked like a strong competitor to Trump after he emerged victorious in Iowa, finds himself in a weakened position after failing to beat Trump or Rubio in last Saturday’s South Carolina GOP primary. It was an especially stinging blow because it raised questions about his plan to dominate Southern states packed with ideological conservatives and evangelicals in the so-called SEC Primary.

“Cruz has the most riding on Super Tuesday,” said Stutts. “His whole strategy really banked heavily on the Southern strategy. Not only does he have to win Texas, he has to find another ‘W’ and take home the most delegates on Super Tuesday.”

While Cruz leads most polls in Texas, he trails Trump elsewhere. The Yellowhammer conservative news website reported that the Texas senator had pulled out of events in Alabama over the weekend in a possible sign his Southern firewall was crumbling.

New polls in two key states on Monday had sobering news for Cruz. In the Monmouth University survey in Alabama, Trump earned the support of 42% of likely GOP primary voters, compared to 19% for Rubio and 16% for Cruz. Trump leads in Oklahoma with 35% in a poll from the same organization, ahead of Cruz at 23% and Rubio at 22%.

Cruz’s team is confident, however, that their boss can rewrite the political narrative Tuesday.

“This is the day that we have spent (the) most time on,” former Virginia Attorney General Ken Cuccinelli, a Cruz supporter, told CNN’s Wolf Blitzer on Friday.

“We are going to win multiple states next Tuesday.”

Should Cruz win in Texas – the state he referred to last week as the “crown jewel” of Super Tuesday because of its 155 delegates – there could also be an upside for Trump.

That’s because a win there would give Cruz a rationale to stay in the race and keep Rubio from coalescing opposition against the Republican front-runner.

“I don’t think it is bad news for Donald Trump if he loses Texas,” said CNN political analyst David Gergen on Thursday. “If he wins most of the other states and loses Texas, he will have momentum coming out of it, and Cruz stays in the race. And he needs Cruz to stay in the race.”

Clinton could see advantage

On the other side of the aisle, the Democratic Super Tuesday clash is not going to force either of the candidates out of the race however it ends.

But it could hand a clear advantage to Clinton as she seeks to exploit the Southern advantage that her campaign has long argued makes it impossible for Sanders to win the nomination.

The former secretary of state will be looking to engineer a sweep of the Deep South, Virginia and Texas and to also be competitive in states where Sanders, a Vermont senator, looks to have his best chance.

That could allow Clinton to build up a lead in delegates before the race heads to Northern and Midwestern states where the Sanders message of an economy rigged against American workers could provide her with a more irksome challenge.

Clinton’s huge win in South Carolina on Saturday was based on a huge outpouring from African-American voters.

That turnout suggests that she will triumph in states voting Tuesday with similar demographic profiles, including Alabama, Arkansas, Georgia, Tennessee and Virginia. Her aides know that she cannot knock out Sanders on Tuesday, but they hope to end the night with a lead of around 100 earned delegates.

Sanders, meanwhile, made clear where his future lies, paying only passing attention to the South Carolina primary on Saturday while spending the day in Texas and Minnesota.

His campaign is making clear that despite the size of his defeat in South Carolina – equal to nearly 50% of the vote – he is nowhere near giving up his campaign, though the candidate himself appears to have rock-bottom expectations in the South.

“I think we got a real shot at Minnesota. I think we got a shot at Colorado, Oklahoma, Massachusetts and Vermont,” Sanders said on NBC’s “Meet the Press” Sunday. “So we’re looking to the future, not looking back.”

A Monmouth University poll of the Democratic race published Monday suggested Sanders is in good shape in at least one of those target states, showing that he leads the former secretary of state by 48% to 43% in Oklahoma.

CNN’z Jeff Zeleny contributed to this report.