WASHINGTON, United States (AP) — Joe Biden decisively won Michigan’s Democratic presidential primary, seizing a key battleground state that helped propel Bernie Sanders’ insurgent candidacy four years ago. The former vice president’s victory there, as well as in Missouri, Mississippi and Idaho, dealt a serious blow to Sanders and substantially widened Biden’s path to the nomination.

Biden again showed strength Tuesday with working-class voters and African Americans, who are vital to winning the Democratic nomination.

Sanders won North Dakota and awaited results from Washington state. Washington’s primary was too early to call, and because all votes there are cast by mail or by dropping them off in a ballot box, many ballots were marked for candidates who have since dropped out of the race.

The six-state contest Tuesday marked the first time voters weighed in on the primary since it effectively narrowed to a two-person race between Sanders and Biden. And the first four states on Tuesday went to Biden, a dramatic reversal for a campaign that appeared on the brink of collapse just two weeks ago. Now it is Sanders, whose candidacy was ascendant so recently, who must contemplate a path forward.

Addressing supporters in Philadelphia, Biden noted that many had “declared that this candidacy was dead” only days ago, but “now we’re very much alive”. He also asked Sanders supporters to back him going forward.

“We need you, we want you, and there’s a place in our campaign for each of you. I want to thank Bernie Sanders and his supporters for their tireless energy and their passion,” Biden said. “We share a common goal, and together we’ll beat Donald Trump.”

It marked a high point for the former vice president’s staff. They sipped beer and broke into an impromptu dance party after his speech, which was held close to his Philadelphia headquarters.

Even as the contours of the race came into shape, however, new uncertainty was sparked by fears of the spreading coronavirus. Both candidates abruptly cancelled rallies in Ohio that were scheduled for Tuesday night. That set the stage for Biden’s remarks in Philadelphia, while Sanders flew home to Vermont and didn’t plan to address the public.

Sanders’ campaign also said all future events would be decided on a case-by-case basis given public health concerns, while Biden called off a scheduled upcoming Florida stop. Still, the former vice president said Tuesday night that he’d be announcing plans to combat the coronavirus later this week.

The Democratic National Committee also said that Sunday’s debate between Sanders and Biden would be conducted without an audience.