On the heels of the Democratic caucus wins over the weekend in three U.S. states, presidential hopeful Bernie Sanders claimed political momentum he hopes will help him stymie the lead held by front-runner Hillary Clinton.

Sanders easily took caucuses in Alaska, Washington and Hawaii on Saturday, wins he hopes will spark a comeback that will chip away at Clinton's commanding lead in the number of delegates needed to win the party's nomination.

His comeback will be an uphill battle.

His overwhelming victories over the weekend netted him 55 delegates to Clinton's 20, but did not significantly eat into her lead. Clinton went into Saturday's caucuses with roughly 300 delegates more than Sanders, which is about double the margin that Barack Obama held over Clinton in the 2008 primaries.

Based on primaries and caucuses results to date, Clinton has won 1,243 delegates to Sanders's 975.

David Spring, leader of a pro-Sanders group in Seattle called Washington for Bernie Sanders, told CBC News that Sanders dominated delegate-rich Washington because it is "a progressive state."

"We were hoping to win by a two-to-one margin," said Spring. "Instead, we won by a three-to-one margin — it was the biggest victory of any presidential caucus in the history of Washington state. In my caucus, Bernie Sanders got 80 per cent of the vote." 

'Hillary Clinton's states are done now'

Sanders may need to win in upcoming contests by the same margins he won by over the weekend in order to gain ground on the former secretary of state.

The senator from Vermont needs to capture 67 per cent of remaining delegates — plus uncommitted superdelegates — in order to surpass Clinton, who will keep piling up delegates even when she loses under a Democratic Party system that awards them proportionally in all states. 

Sanders has been winning 37 per cent of pledged delegates so far.


Including superdelegates, Hillary Clinton has 1,712 delegates to 1,004 for Sanders, according to a tally by RealClearPolitics.com. (Justin Sullivan/Getty Images)

Spring believes Clinton's lead is due to the early nomination battles being held in conservative battlegrounds, which he says unfairly benefits Clinton.

"I think it is important that everybody understand that the Democratic National Committee has attempted to rig the election in favour of Hillary Clinton by having the conservative states vote first," said Spring. "All of Hillary Clinton's state are done now … from here on in Bernie Sanders is going to run the table."

Sanders needs superdelegate support

Interviewed on Sunday by U.S. broadcasters, Sanders said Democratic superdelegates, who can change their allegiance, might rally behind him because some polls suggest he has a better chance than Clinton of beating a Republican candidate.

"Momentum is with us. A lot of these superdelegates may rethink their position with Hillary Clinton," said Sanders on CNN'S State of the Union news program.

Feeling the Bern in B.C.5:21

About 85 per cent of the votes at the July 25-28 Democratic National Convention in Philadelphia, where a party nominee will be chosen to face the Republicans in the Nov. 8 election, are being determined by state nominating contests.

The other 15 per cent is held by party power brokers who are free to vote as they like, meaning they could hold the key in a tight contest.

Superdelegates include party leaders and elected senators, members of the U.S. Congress and governors. The system was adopted in the early 1980s to give party leaders more control over the nominating process.

"The superdelegates are going to have to make a very difficult decision," Sanders said on ABC's This Week With George Stephanopoulos.


Sanders has won support from young people and white, working-class voters with his calls for breaking up Wall Street banks and making tuition free at public colleges and universities. (Scott Olson/Getty Images)

After Saturday's contests, the former secretary of state led Sanders by just under 300 pledged delegates in the race for the 2,382 needed to be nominated.

Adding in the support of superdelegates, Clinton had 1,712 delegates to 1,004 for Sanders, according to a tally by RealClearPolitics.com.

RealClearPolitics averages of polls show Sanders with a small edge over Clinton in a hypothetical contest against Republican front-runner Donald Trump.

Sanders said party leaders in states where he has won decisively will come under pressure to back him whether they have pledged to support Clinton or not, and urged superdelegates to consider polls in which Americans are presented with potential battles between various presidential hopefuls.

Rex Murphy: Trump and Sanders as 'the anti-candidates'3:16

Spring agrees, saying Sanders is the only Democratic candidate who can draw support from on-the-fence voters and beat Trump in a general election.

"I talked to hundreds and even thousands of independent voters and I am having trouble finding any that vote for Hillary Clinton," said Spring, noting "massive numbers" of independents he talked to would vote for Trump if Clinton were to be the Democratic nominee.

"This is where the Democratic Party needs to wake up," he adds. "If Bernie Sanders is not the Democratic candidate, I think we are looking at Donald Trump for the next president of the United States."

With files from Reuters and The Associated Press