Bernie Sanders is about to face a do-or-die stretch to keep up with Hillary Clinton

On Sunday evening, Hillary Clinton’s campaign released a video of staffers celebrating the former secretary of state’s five-point win in last weekend’s Nevada caucuses.

“H-R-C! Twenty-sixteen!” they chanted, jumping up and down.

Clinton only picked up four more delegates than Sanders in a state long seen as more favourable to her. But the campaign had good reason to be relieved.

Sanders’ failure to break through Clinton’s so-called “firewall” in Nevada represented a key rupture in the senator’s campaign strategy, at a time when the electoral map becomes far more favourable for Clinton.

According to recent polls, Clinton has a significant advantage in the 12 states set to hold contests over the next two weeks. Those states will award a sizeable chunk of the 2,383 delegates needed to secure the Democratic presidential nomination.

“She could effectively end the race in less than two weeks’ time on Super Tuesday,” David Wasserman, an analyst with The Cook Political Report, told The New York Times.

Clinton retook the lead from Sanders in pledged delegates after the Nevada caucuses. She now has a 52-51 advantage. And many of the southern states weighing in over the next week appear, at the moment, like virtual locks for Clinton.

She leads in every major recent poll in South Carolina, where the state’s majority-black Democratic electorate is overwhelmingly in favour of Clinton. Democrats in the Palmetto State vote Saturday.

Meanwhile, a series of Public Policy Polling surveys from earlier this month showed Clinton with almost 30-point leads over Sanders in Alabama, Arkansas, Georgia, Tennessee, Texas, and Virginia. Clinton also held a comfortable lead in a late-January poll in Minnesota, where Sanders told NBC’s Chuck Todd on Sunday that the senator would be competitive. Voters in those states all weigh in on “Super Tuesday,” March 1.

There are a few bright spots on the map for Sanders, however.

The senator is likely to rout Clinton in his home state of Vermont, where the latest poll showed Clinton with just 10% support. At least one recent poll found the senator running ahead of the former secretary of state in Colorado, where he’s also secured a congressional endorsement. And polls have shown the two candidates running neck and neck in Massachusetts and Oklahoma.

Until contests in mid-March, Democratic delegates in Democratic primaries are awarded proportionally, based on wins in certain districts. So victories in big states matter more in terms of perception than as a means to securing the nomination.

But as The New York Times reported, even Sanders’ campaign recognises that the delegate maths may not play to Sanders’ advantage. Senior Sanders campaign adviser Tad Devine suggested to The Times that Sanders’ path to the nomination would likely require a string of upsets — as well as a lobbying campaign to convince already-pledged Clinton “superdelegates” to support Sanders.

“The Clintons can get a delegate lead quicker than we can, and they have a way to gut out the delegate fight,” Devine told The Times. “We have to turn victories in state after state into big momentum that can change the numbers.”

After Super Tuesday, the senator’s uphill March battle could get even tougher.

If Clinton maintains her large leads among older and minority voters, particularly black voters, exit polls from 2008 suggest she would have a demographic advantage in winner-take-all states like Ohio, Illinois, Florida, and Missouri.

And as Politico reported Monday, event the dates of the primaries are bad luck for Sanders.

Many of the major nominating contests in March fall during spring break for large universities, making it difficult for the campaign to organise a large turnout from major college campuses.

Though students don’t typically make up a large percentage of voters, they can make the difference in key districts.

Former staffers on Sen. Rand Paul’s failed presidential bid suggested to Business Insider earlier this year that former Rep. Ron Paul, Rand’s father, may have won the popular vote in the 2012 Iowa caucuses if several major universities hadn’t been on winter break.

Instead, he was outpaced by Republican candidates Rick Santorum, the eventual winner of the caucuses, and Mitt Romney, the eventual nominee.

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