Watch Kane Farabaugh's report from Illinois

CHICAGO - As he ascended the stage on a sunlit, unseasonably warm March afternoon, Bernie Sanders, running for the Democratic nomination for president, basked in the adoration of thousands of supporters huddled together at Chicago's historic Grant Park.

"Thank you Chicago!" he beamed.  "I can't even see the end of the crowd you are so far back!"

Before concerns about the spread of the COVID 19 virus forced organizers to abandon similar large events, rallies like this one in Chicago were a hallmark of Sanders' campaign, attracting legions of younger supporters like nurse Sabrina Hornak, who is enthusiastically backing the Vermont senator in the Illinois primary election set for Tuesday.

"I feel great about the turnout here today," she told VOA while standing behind one of the temporary fences put up for the large crowd that gathered to see Sanders speak.

"I think it bodes really well for the primary," she said.

However, even before COVID 19 concerns, crowd size wasn't translating into success at the ballot box for Sanders.

Now the front runner, former Vice President Joe Biden is already trying to reach out to those backing Sanders.

"And I want to thank Bernie Sanders and his supporters for their tireless energy and their passion," Biden told reporters at the National Constitution Center in Philadelphia after securing decisive election wins March 10.  "We share a common goal and together we'll defeat Donald Trump," he said.

Despite cancellation of most U.S. political events because of the COVID 19 virus, four more states hold presidential nominating contests Tuesday that could virtually eliminate any doubt as to who will face President Donald Trump for the Democratic Party in November. 

Biden is widely expected to add to his delegate lead over Sanders when votes are cast in Florida, Ohio, Illinois and Arizona.

However, in his message to voters in Chicago March 7 in what was one of his last public campaign appearances in Illinois, Sanders wasn't giving up.

"And if we're going to beat Trump," Sanders told the crowd, "we need the largest voter turnout in the history of America, and that turnout looks like Grant Park today!"

While it's not certain how the spreading virus will affect voting in the contests ahead, turnout is up in many states where primary election ballots have already been cast, and exit polling shows Sanders with strong support from voters aged 18 to 29.  

Those voters, though, aren't turning out in large enough numbers to overcome the advantage older voters gave former Biden in a number of victories in key states.

"I think apathy has a lot to do with voting," Hornak said, adding, "When it comes to the youth… a lot of young people think nothing is going to make a difference.""

In 2018 people were surprised by it," says Illinois State University politics and government professor Julie Webber, referring to the 2018 midterm elections in which Democrats regained control of the House of Representatives.  "I think 1 in 5 nationwide young people voted, which was unprecedented, but so far the Sanders camp has been pretty disappointed with the youth voter turnout."

Polling data also show many voters see Biden best suited to defeat Trump, something many Democrats prioritize over specific policy positions on issues such as health care reform and making college affordable.

"There's a kind of confusion going on in the American electorate about that," Webber told VOA from her office on the ISU campus in Bloomington, Illinois.  "Trying to hedge your bet against a winner, because people see the stakes so high on the Democratic side against Donald Trump, versus really voting for what you actually want to see put into practice in policy preferences."

"I think it's really going to come down to a choice between the future and the past," said Sanders supporter Miles Kampf-Lassin.

"We can't sugarcoat things," he told VOA after Sanders' Chicago rally.  "We should be sober.  Super Tuesday didn't go the way many Sanders supporters and the campaign were expecting."

Sanders narrowly lost Illinois to Hillary Clinton in the 2016 primary election, and polls show Sanders trailing Biden in all four states voting Tuesday.

"I feel this race is far from over," said Kampf-Lassin.  "When you look at all the people who were signing up for canvass shifts… when you see the amount of donations that are going into the Bernie Sanders campaign right now… I think it shows that people are not ready to give up this fight."

Sanders' campaign desperately needs a surprise victory or two to be seen as viable going forward. 

Biden, meanwhile, is increasingly focusing his firepower on Trump, blasting his response to the COVID-19 crisis.

"This virus laid bare the severe shortcomings of the current administration," Biden said in prepared remarks to reporters in his hometown of Wilmington, Delaware.  "Public fears are being compounded by pervasive lack of trust in this president.  And our ability to drive a global response is dramatically, dramatically undercut by the damage Trump has done to our credibility and our relationships around the world," he said.

As the primary election contest to select a Democrat to challenge  Trump in November continues this spring, if Sanders falls short, Hornak said she will support Biden because "anything is better than Donald Trump at this point."