Democratic presidential hopeful Bernie Sanders Bernie SandersSenate Republicans signal openness to working with Biden Hillicon Valley: DOJ indicts Chinese, Malaysian hackers accused of targeting over 100 organizations | GOP senators raise concerns over Oracle-TikTok deal | QAnon awareness jumps in new poll Schumer, Sanders call for Senate panel to address election security MORE on Sunday said the Iowa caucuses could mark the beginning of one of the biggest electoral upsets in U.S. history.

“Well, Jake, you know, when we started this campaign here in Iowa, we were 50 or 60 points behind Secretary Clinton,” Sanders told host Jake Tapper on CNN’s “State of the Union.”

“We have come a long, long way,” he added. “And the reason for that is, we have 15,000 volunteers who today are going to be knocking on doors. They're going to be making telephone calls. They're going to be urging people in very large numbers to come out and vote.”

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“So, I'm feeling good, Jake. Our issues are out there. People are really enthusiastic. And if people come out to vote, I think you're going to look at one of the biggest political upsets in the modern history of our country.”

He said if enough people turn out to caucus, then “we have got a real shot to win this.”

Sanders is neck and neck with Democratic front-runner Hillary Clinton Hillary Diane Rodham ClintonBarr criticizes DOJ in speech declaring all agency power 'is invested in the attorney general' Virginia Democrat blasts Trump's 'appalling' remark about COVID-19 deaths in 'blue states' The Hill's Campaign Report: Biden asks if public can trust vaccine from Trump ahead of Election Day | Oklahoma health officials raised red flags before Trump rally MORE.

A new Bloomberg/Des Moines Register poll released on Saturday has the Vermont senator trailing by just 3 points in the first-in-the-nation caucus, within the poll’s margin of error.