Mr Sanders yesterday said that Democratic "super-delegates", who can change their allegiance, might rally behind him because some polls suggest he has a better chance than Ms Clinton of beating a Republican candidate.
Fresh from Democratic presidential primary wins in three USA states, Bernie Sanders says he had political momentum that could help him win the backing of Democratic powerbrokers in his race against Hillary Clinton. Senior Sanders adviser Tad Devine has said for weeks that superdelegates could flip to Sanders if the campaign can prove he's stronger than Clinton in a general election and can expand the party's base of support in the fall. That is what the American people want to hear.
The wins weren't too surprising, since the states have a large population of white, working-class, liberal voters that tend to vote for Sanders. In total, Sanders earned 55 delegates Saturday to Clinton's 20, the AP reported.
Clinton has 1,243 nominating delegates pledged to her, compared with Sanders' 975, according to the Associated Press.
However, Sanders has vowed to stay in the race until all 50 states have voted.
The Vermont senator also kept up his attack on Clinton for her attending a fundraiser hosted by George and Amal Clooney, with a price tag of more than $353,000 per couple to sit at the head table. To secure the nomination, 1,237 delegates are needed.
It was a good weekend for Democratic presidential candidate Bernie Sanders and his supporters.
Sanders, for his part, appeared Sunday to challenge Clinton to an additional debate in NY.
Bernie Sanders' campaign laid out their plan for winning the Democratic nomination, despite Hillary Clinton's lead among pledged and at-large delegates.
ABC News calculates that Sanders needs to win 73 percent of the remaining delegates in order to capture the nomination. Democrats compete next on April 5 in Wisconsin and again April 9 in the sparsely populated state of Wyoming.
"A national poll just came out that had us 1 point ahead of Secretary Clinton, when we started 60 points behind", he added.