After a string of primary losses, Vermont senator Bernie Sanders took the state of Indiana, the victory generating some momentum for his campaign as the primary season enters its final phase.
Tuesday's win offers "another sliver of hope for Sanders supporters in California, which would keep them from resigning themselves to the inevitable Clinton victory", said Dr Aaron Dusso, assistant professor of political science at Indiana University - Purdue University Indianapolis.
Only 13 Democratic contests remain, including California, which offers the largest delegate haul.
Despite the loss, front runner Hillary Clinton still maintains a large lead of 2,220 delegates over Mr Sanders' 1,449, according to the New York Times and the Associated Press. She is closing in on the 2,383 delegates needed to clinch the party's nomination at the national convention in July.
Mrs Clinton continues to focus her campaign on presumptive Republican nominee Donald Trump, calling on supporters to help her beat him in the general election.
"Donald Trump is the presumptive GOP nominee. Chip in now if you agree we can't let him become president," she tweeted.
While some in the Democratic establishment have urged Mr Sanders to end his campaign, he has said it will go all the way to the end.
In an interview with CNN after Tuesday's results, Mr Sanders argued that it would be "irresponsible and undemocratic" if voters in the remaining states were not given a chance "to be heard".
He reiterated that his strategy is to stay in the race and, ultimately, convince superdelegates - mostly party officials - that they should vote for him instead. Mrs Clinton currently has the support of 520 superdelegates, while he has only 39.
But experts are less optimistic that delegates will gravitate towards Mr Sanders.
"Losing campaigns often tend to overcommit to over-optimistic scenarios," said public affairs lecturer John Karaagac from Indiana University, Bloomington.
Barring any serious legal charges that might complicate Mrs Clinton's path to the White House, superdelegates will "stick with her... knowing this is the best they have this cycle", he added.
Mr Sanders also believes he is the stronger candidate against Mr Trump, as he has a stronger following among independent voters.
Staying doggedly in the race may help or hinder the party depending on how one looks at it, say experts.
"The traditional critique is that a long primary drains the presumptive front runner of precious resources, energy and money.
Far better to pivot to a general election earlier and sooner," said Dr Karaagac.
However, he added that "if the voters think the Democratic Party should be pulled to the left, then he (Sanders) is helping the party".
Mr Sanders also told CNN he is energising the party base, especially among young voters.
Said Dr Dusso: "If he can keep large numbers of individuals energised for the election, he will likely help the Democrats in November."