With Donald Trump now the presumptive Republican nominee, attention is shifting to the Democratic race. The contest between Hillary Clinton and Bernie Sanders is more about the party's values than about the nomination.
Even if Senator Bernie Sanders loses the battle for the Democratic presidential nomination, he could well win the fight for the party's future and have a major influence on the direction of US politics.
When Sanders launched his campaign last year, he was something of a political curiosity: an independent senator from the small state of Vermont and a self-identified democratic socialist.
Socialist is normally an insult in US political parlance.
But Sanders has proven to be a major political force since voting began in February. He has won 18 states and is about 300 pledged delegates shy of former Secretary of State Hillary Clinton's lead.
The senator has mobilized a grassroots movement of predominantly young and working-class people. Since the start of his campaign, he has raised $182 million (160 million euros) from millions of individual small donors.
John Nichols, a reporter for The Nation magazine, has covered Sanders for 25 years. He said the senator would likely have enough delegates to contest the convention and pressure the center-left party to adopt a more progressive agenda.
"Some of the most interesting contested conventions have not been fights for the nomination," Nichols told DW. "They have been fights to define the platform, values and program of a political party."
The Nation, a progressive publication, has endorsed Sanders in the Democratic race.
'Difficult and narrow'
After a string of defeats in four Northeastern states, Sanders vowed to fight on and has been buoyed by a surprise upset in Indiana. But his chances of winning the nomination are increasingly thin.
"It is a difficult and narrow path to the nomination," said Neil Sroka, the communications director at Democracy for America, an advocacy group that backs Sanders.
The senator has struggled to garner support among African-Americans and Latinos. And while the pledged delegate count might look fairly competitive, Clinton has a huge lead in superdelegates.
The 714 superdelegates are elected officials and party luminaries who aren't bound by the outcome of their state primaries. They are free to back the candidate of their choice at the nominating convention.
When superdelegates are included in the count, Clinton is fewer than 200 shy of winning the nomination outright and facing the presumptive Republican nominee, Donald Trump, in November.
"Hillary Clinton has an overwhelming advantage," Nichols said.
Which isn't to say that the former secretary of state would be finished with Sanders. His backers are trying to gain as much leverage as possible to force negotiations with Clinton.
"We are working closely with Senator Sanders to ensure that he can acquire as many delegates as possible going into this convention," Sroka said. "In doing so, [we hope] to ensure the grassroots movement he has built has a strong and powerful voice at this convention and make sure our issues are at the very center of Democratic Party," he added.
During the campaign, Sanders has delivered a progressive economic message to great effect, vowing to fight what he calls the "billionaire class" and restore the middle class by reducing income inequality. His message has already pushed Clinton to the left on issues such as trade and raising the minimum wage.
When she served as secretary of state under US President Barack Obama, Clinton backed the Trans-Pacific Partnership, a trade deal that would encompass 40 percent of the global economy. During the early leg of the campaign, however, she fell silent as Sanders railed against the agreement as a threat to American jobs. Clinton has since come out against TPP.
"The biggest question going forward is holding Secretary Clinton, should she be the nominee and hopefully our president, accountable for the promises she's made during the primaries," Sroka said.
The candidates have also been caught in a bidding war over how much the federal minimum wage should be raised from the current $7.25. Clinton supports a $12 floor, while Sanders has called for $15. At the state level, New York and California, two heavyweights of the US economy, have already voted to gradually raise their minimums to $15.
Nichols said Sanders supporters could cements aspects of the senator's populist message in the Democratic platform and force a debate on more contentious issues, such as public health care and tuition-free college.
"If Hillary Clinton has most of the delegates, she isn't going to accept a full Sanders platform," Nichols said. "By the same token, if she and her supporters accept elements of a Sanders platform, it could end up in a situation that unifies the party and makes it a stronger player going into a fall election."