With Hillary Clinton sweeping all five primary contests on Tuesday, the math is looking grim for Bernie Sanders to have any hope of making up the difference in delegates he’ll need to secure the Democratic nomination. The campaign now moves west into states which could be more favorable to Sanders, though Hillary Clinton’s delegate lead may soon become insurmountable.

Report from USA Today:

Sen. Bernie Sanders says he still sees a path to the Democratic presidential nomination, even after Hillary Clinton won at least four more nominating contests on Tuesday.

Sanders is pinning his hopes on contests coming up in the West.

“With more than half the delegates yet to be chosen and a calendar that favors us in the weeks and months to come, we remain confident that our campaign is on a path to win the nomination,” he said in a statement.

Sanders believes his campaign, fueled by passionate supporters donating online, can continue until final contests in June. He will hold events this week in Arizona, Idaho and Utah, where voters will go to the polls on Tuesday and where Sanders expects to do well. His campaign also sees opportunities in Alaska, Hawaii and Washington state, which hold caucuses the following Saturday, on March 26.

But the Vermont independent’s path forward looks less likely, mathematically, after Clinton’s victories Tuesday in Florida, Illinois, North Carolina, and Ohio marked an apparent turning point in the campaign. On Wednesday, the primary in Missouri remained too close to call, with Clinton up by just 1,531 votes out of 619,673 cast.

Clinton now has 1,139 pledged delegates to Sanders’ 825. When counting superdelegates, who are free to support the candidate of their choice, the former secretary of State is only 777 delegates short of the 2,383 needed to clinch the nomination. Sanders is 1,532 delegates short. [Emphasis added]

The Sanders campaign believes superdelegates will follow the will of voters if he wins future contests. In terms of pledged delegates, this is the “high water mark” for Clinton’s campaign and Sanders will soon begin to erode that advantage, Sanders’ campaign manager, Jeff Weaver, said Wednesday.

The next few contests will be crucial for Sanders to start accumulating more delegates. The biggest hurdle he faces, however, is simply the way that all of the Democratic primary contests are awarded proportionally. That means that even a string of victories by Sanders will still let Clinton accumulate delegates at the same time.

Sanders is correct, the superdelegates would follow him if he started winning more states and overtook Clinton’s pledged delegate lead, similar to what happened in 2008. However, the problem for Sanders, is that the math and ticking clock says that with each contest, that gets harder and harder.

While not impossible, it’s unlikely at this point that Sanders can win enough states by a high enough margin to make serious inroads toward Hillary Clinton’s pledged delegate count.