Democratic presidential contenders Joe Biden and Bernie Sanders were left to reassess how to campaign in the face of a spreading US coronavirus outbreak on Wednesday, after the former vice president nearly swept a big day of nominating contests. 

Former vice president Joe Biden Photo: VCG

The two candidates canceled election night rallies on Tuesday, citing recommendations from public health officials to avoid assembling large indoor crowds. 

Joe Biden moved a giant step closer on Tuesday to a November showdown with Donald Trump, notching up big primary wins over Bernie Sanders, his sole remaining challenger for the Democratic presidential nomination. 

Biden, 77, the centrist former vice president, scored a resounding win in Michigan, where Sanders, 78, the leftist senator from Vermont, had hoped to make a stand. He also cruised to victory in Missouri, Idaho and Mississippi. 

Addressing supporters in Philadelphia as his victory took shape, Biden struck a presidential tone as he declared on national television that he would lead "a comeback for the soul of this nation." 

"We're bringing this party together," he said. "Tonight we're a step closer to restoring decency, dignity and honor to the White House." 

Biden reached out to his sometimes bitter rival Sanders and his supporters, telling them "we share a common goal." 

"Together we'll defeat Donald Trump," he said. 

Biden's huge victory in Mississippi, where he won around 80 percent of the vote, reflected his popularity among strategically vital African American voters. He defeated Sanders by 25 points in Missouri. 

His win in Michigan, the Midwestern industrial state which could be a key battleground in November, was a major setback for Sanders, who narrowly beat Hillary Clinton there four years ago. 

Sanders led the count by less than 2,000 votes in Washington state, the other major prize of Tuesday's primaries, with around 70 percent of the vote counted on Wednesday morning. He was also leading by six points in North Dakota. 

Barring surprises, Biden now has a clear path to becoming the Democratic standard-bearer in a potentially bruising and deeply divisive matchup with Trump. 

The main question remaining is whether Sanders will fight to the bitter end as he did four years ago against Clinton or bow out early. 

Sanders did not immediately address Tuesday's results.


Newspaper headline: Biden notches more US primary wins