The NPR/PBS NewsHour/Marist Poll puts him 12 points ahead of his nearest rival, Michael Bloomberg, who will now be joining Sanders and the other primary candidates on the debate stage for the first time.
Mr Sanders’s support has grown since he won the New Hampshire primary, where he narrowly defeated former South Bend mayor Pete Buttigeig. He continues to draw huge crowds at his rallies, and last year raised roughly $96m from more than 5 million contributions.
However, Mr Sanders faces challenges headed into the next primaries. His campaign for the upcoming Nevada caucuses has been overshadowed by protests from the powerful Culinary Workers Union, the state’s largest labour organisation, which opposes his “Medicare for All” plan.
On the other hand, there are signs he is overcoming his past weaknesses as a candidate, in particular by attracting more support from voters of colour.
Meanwhile, several other candidates once expected to win or run strongly in the primary show further signs of falling behind. Joe Biden has dropped from 24 per cent to 15 per cent, while Elizabeth Warren has fallen to just 12 per cent.
Mr Buttigeig, who ran neck-and-neck with Mr Sanders in Iowa and came second in New Hampshire, languishes on just 8 per cent, while the newly ascendant Amy Klobuchar has apparently overtaken him, now sitting at 9 per cent.