Joe Biden has won Ohio's presidential primary, which was conducted by mail, CBS News projects. As of 8:30 p.m. ET, Biden had picked up 74 of Ohio's 136 pledged delegates. The rest of the delegates will be awarded as more votes are counted. So far, Biden has won 72% of the vote — 623,186 of the 860,347 ballots counted at this point, according to Ohio's secretary of state. Bernie Sanders won 17% support — he dropped his presidential bid in April, weeks after the primary was originally to take place.

Governor Mike DeWine delayed the primary, which had been scheduled for March 17, amid concerns about the coronavirus. Tuesday's results were a test of the ability of states to handle elections, including the upcoming general election. Several states have been trying to put together last-minute vote-by-mail primaries amid the coronavirus pandemic.

DeWine delayed the Ohio primary hours before polls were set to open on March 17, citing concerns about the spread of the virus. Voters were encouraged to instead vote by mail with a deadline of April 28. More ballots are still expected — those postmarked by April 27 must be received by May 8 to be counted. Voters were also allowed to drive to their county board of elections to their ballot in a secure drop box before 7:30 p.m. on Tuesday.

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DeWine's announcement prompted legal challenges and some confusion when a judge initially denied his request to delay the primary. DeWine then said that polls would be closed due to a health emergency, with the order coming from the Ohio health director. The Ohio state legislature then passed legislation that extended the vote-by-mail deadline to April 28.

A Cuyahoga County Board of Elections worker drops a ballot in the box outside the Cuyahoga County Board of Elections during Ohio's primary on Tuesday, April 28, 2020, in Cleveland. Tony Dejak / AP

Some in-person voting on Tuesday was allowed, although only to individuals with disabilities or those without permanent mailing addresses. Ohio Secretary of State Frank LaRose announced Monday that over 1.9 million Ohioans had requested a vote-by-mail ballot, and over 1.4 million had already cast their vote.

"In a matter of weeks, we've done something that's taken other states years to do — transform our state into one capable of voting entirely by mail," LaRose said in a statement.

At a press conference on Tuesday, LaRose said the U.S. Postal Service told him that the postal service was delivering 17,000 ballot envelopes to the Cuyahoga County Board of Elections, which is home to Cleveland, and 10,000 ballot envelopes to the Hamilton County Board of Elections, where Cincinnati is located.

"This is not what any of us had envisioned months ago for how we wanted to run this election. But Ohio's boards of elections, these bipartisan teams of very dedicated and patriotic individuals in all 88 counties, have risen to the occasion," LaRose said.

In Franklin County, where Columbus is, 725 people had voted in person as of 3 p.m. Tuesday afternoon, according to Board of Elections public information officer Aaron Sellers. Sellers told CBS News that the county Board of Elections received about 18,500 ballots at its secure dropbox and delivered from the post office, leaving around 25,000 ballots outstanding.

Several states have delayed their primaries or resorted to vote-by-mail due to concerns about the pandemic. New York on Monday canceled its primary altogether. Voting rights activists have also called for Congress to provide more funding for states to implement greater access to vote-by-mail.

Jack Turman contributed to this report.