Biden was already the presumptive presidential nominee, after Bernie Sanders suspended his campaign. Wisconsin controversially held in-person voting despite the pandemic.
Though the Vermont senator did not emerge as the Democratic nominee in either of his two bids, his campaigns have reshaped the party's politics and policy in significant ways.
Gov. Tony Evers tried to postpone voting and extend the absentee deadline, but he was blocked by courts. Results for Tuesday's contests are not expected for days.
It looked like Sanders was about to drop out of the Democratic primary, until the coronavirus crisis gave his agenda a boost and turned his campaign into a relief drive. But what's next?
Coronavirus is dominating. Three of four crucial states are going ahead with elections Tuesday that could determine the Democratic presidential nominee.
Louisiana and Georgia have postponed their presidential primaries, but the four states scheduled to vote on Tuesday say they are moving forward. Here's what they're doing to keep voters safe.
The first one-on-one debate between the two men was supposed to be in Arizona, one of four states voting in the Democratic presidential primaries Tuesday. But it took place in a TV studio instead.
As the coronavirus pandemic spreads across the country, former Vice President Joe Biden and Sen. Bernie Sanders will debate Sunday night in Washington with no live audience.
The Democratic presidential candidate said the president's decisions and cuts have left the country "woefully unprepared." The former vice president vowed his administration would "lead by science."
Joe Biden invited his opponent's supporters to join him. Bernie Sanders responded with a road map and challenge for the front-runner to meet at the next debate.
Exit polls show that while men were about evenly divided, women in Michigan heavily preferred Biden. And across states, young voters — key to Sanders' past success — failed to turn out in a big way.
In a press conference, the Vermont senator acknowledged calls for him to drop his bid for the Democratic presidential nomination but said he plans to debate former Vice President Joe Biden on Sunday.
Joe Biden increased his delegate lead with the March 10 primaries, and a top Democratic super PAC concluded he's on track for the nomination. Bernie Sanders didn't say what's next for him.
As the number of confirmed coronavirus cases continues to climb, election officials and candidates are weighing how to make sure the political process doesn't become the next casualty of the virus.
As vice president, Biden visited Detroit nearly a dozen times, more than President Barack Obama. He was in Detroit again on Monday, this time campaigning before Michigan's Tuesday primary.
Tuesday's contests offer 352 delegates among six states. Michigan is the biggest prize, and it could be another pivot point in this Democratic primary.