Former Vice President Joe Biden is now overwhelmingly expected to win a majority of pledged delegates before the Democratic National Convention, according to FiveThirtyEight's primary forecast.

FiveThirtyEight, founded by polling guru Nate Silver, had predicted for many weeks that the most likely outcome of the primaries would be that no candidate earns enough pledged delegates to clinch the nomination. But Biden surged in the forecast after his massive Super Tuesday delegate haul and is now predicted to have a 96% chance to win a majority of delegates.

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The forecast now shows just a 4% chance that no candidate will win enough delegates to win the nomination on the first ballot, which could at least hypothetically send the convention to a second ballot for the first time since 1952. Sanders has said that he would support Biden as the nominee if he goes to the convention with a plurality but not a majority of pledged delegates. Biden has not said he would back Sanders if the latter had a plurality. The forecast gives Sanders and Rep. Tulsi Gabbard, D-Hawaii, less than a 1% chance to win the necessary number of delegates.

Biden currently leads with 664 pledged delegates while Sanders is at 573 in the latest Associated Press count. Some delegates from Super Tuesday are yet to be allocated.

While Biden's lead is certainly not insurmountable, polls released since Super Tuesday show that the race has changed dramatically from the brief period Sanders seemed like an unstoppable frontrunner after winning the popular vote in Iowa, New Hampshire and Nevada.

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A new Morning Consult poll and the latest CNN poll both show Biden leading Sanders by 16 points nationally. Though Biden led the national polls for most of the previous year, Sanders had led in nearly every national poll taken in February.

Sanders hopes to change the narrative on Tuesday, as voters in Michigan, Washington, Missouri, Idaho, Mississippi and North Dakota head to the polls.

Michigan was a key state in the 2016 Democratic primary fight. Former Secretary of State Hillary Clinton led Sanders by more than 21 points in Michigan polls, but Sanders eked out a win by about one percentage point in a major upset.

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Polls similarly show Biden leading Sanders by an average of 25 points, according to RealClearPolitics.

In 2016, pollsters underestimated youth turnout and support for Sanders, as well as the number of independents who voted in the Democratic primary and the number of Democrats who chose to vote in the Republican primary, FiveThirtyEight noted. Pollsters also had little past data to work with because former President Barack Obama did not appear on the Michigan ballot in 2008 and the state had previously held caucuses. This time, pollsters have taken the 2016 electorate into account, and the numbers still show Sanders losing by a large margin.

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Polls do not look much better in other states. Sanders dominated in Washington in 2016 when the state held a caucus but current polling show him in a virtual tie with Biden in the state's upcoming primary. Sanders finished in a virtual tie with Clinton in Missouri in 2016 but two new polls show Biden leading by more than 20 points in the Show-Me State.

The map does not improve for Sanders in the states coming up next week. Biden leads Sanders by double-digits in Arizona and by as much as 41 points in the latest polls out of Florida.

"The Democratic primary could easily turn out to be a fight to the finish after all, but I think people are so used to close elections that they forget that a fair number of them turn out to be anticlimactic," wrote Nate Silver. He later added, "A lot of new polls coming in and they are not promising for Sanders's hopes of keeping the race competitive. He had better hope for a polling miss on Tuesday in Michigan and other states."