Bernie Sanders is about to face a brutal stretch of races against Hillary Clinton

Bernie Sanders is about to face an uphill battle that will test his presidential campaign’s ability to keep up with Hillary Clinton.

On Saturday, Democratic primary voters head to the polls in South Carolina, where all signs point to a likely landslide win for Clinton, the first of her campaign thus far.

Recent polls of Democratic voters in South Carolina gave the former secretary of state a more than 25-point lead over Sanders.

Saturday’s primary comes as Sanders has struggled to overcome Clinton’s advantage in coming primary states among minority voters, which her campaign has long seen as its so-called firewall against Sanders’ rise.

The senator’s loss in Nevada last week represented a key rupture in the Sanders’ campaign strategy, at a time when the electoral map becomes far more favourable for Clinton.

According to recent polls, Clinton has a significant edge 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 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 to 51 advantage, and far more “superdelegates,” the term used to describe Democratic party leaders who have independent votes in the nomination fight. And many of the Southern states weighing in over the next week appear, at the moment, like easy wins for Clinton thanks to their relatively diverse Democratic electorates.

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 Sanders ahead of the former secretary of state in Colorado, where he’s also secured a notable 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 the primary races are awarded proportionally, based on wins in certain districts. So victories in big states matter more in terms of perception than as a means of securing the nomination.

But even Sanders’ campaign recognises that the delegate maths may not play to his advantage. The senator has all but conceded South Carolina to Clinton, spending much of the week leading up to the primary campaigning in Michigan, Oklahoma, and Minnesota.

A top Sanders campaign adviser, Tad Devine, suggested to The New York 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.

Bernie Sanders Hillary ClintonPBSBernie Sanders and Hillary Clinton at a debate.

“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, even 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.

“We’ve seen a lot of enthusiasm for his candidacy,” Mitch Stewart, a veteran field organiser from the Obama campaigns, told Politico. “This is an instance where enthusiasm alone might not be enough.”

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