WASHINGTON (AP) -- After primaries and caucuses in 42 states and the District of Columbia, Joe Biden has won the last few delegates needed to clinch the Democratic nomination for president as states worked to tally a surge of mail ballots.
Indiana, Pennsylvania and Rhode Island were among the seven states, plus the district, holding elections Tuesday. But a huge increase in vote-by-mail ballots, driven in large part by the coronavirus pandemic, meant election officials were still counting ballots Friday.
Democrats don't hold winner-take-all contests in which the top vote-getter wins all the delegates. Instead, the delegates are split up proportionally among the candidates based on their share of the vote -- both statewide and in individual congressional districts.
As the states that voted Tuesday updated their results, a team of analysts at The Associated Press parsed the votes into the correct congressional districts so the delegates could be allocated between Biden and Bernie Sanders.
The process led the AP to allocate 21 delegates to Biden late Friday, after it completed an analysis of votes released by election officials in the three states earlier in the evening. AP later added two more to Biden's total, after the release of additional results in New Mexico.
The former vice president now has a total of 1,995 delegates. It takes 1,991 delegates to win the nomination on the first ballot at the Democratic National Convention.
Biden became the party's presumptive nominee two months ago, following decisive wins over Bernie Sanders in several March primaries and in Wisconsin on April 7. The Vermont senator, the final major challenger in the race, dropped out the next day.
Biden would have wrapped up the Democratic nomination much earlier, if not for the coronavirus pandemic -- 15 states, along with Guam and Puerto Rico, postponed their nominating contests due to the outbreak.
The formality of reaching 1,991 was also delayed by a deal Biden's campaign cut with Sanders in an effort to build Democratic Party unity and avoid the bitter feelings that marred the party's 2016 convention and helped lead to Hillary Clinton's defeat. The agreement allowed Sanders to keep about 300 delegates he would have otherwise forfeited under party rules after suspending his campaign.
It's not unusual for a Democratic nominee to clinch the party's nomination in early June. That's when Barack Obama in 2008 and Clinton in 2016 reached the milestone.
Both Obama and Clinton still had active opponents when they did so, although they were helped by superdelegates. Those are the Democratic Party leaders and elected officials who can vote for any candidate, regardless of the outcome of the primaries.
While superdelegates have never overturned the will of primary voters, their power was greatly reduced ahead of the 2020 election in a concession to Sanders supporters who saw them as undemocratic.
About 800 superdelegates can still participate in this summer's convention, but they won't be able to vote on the first ballot unless their votes would have no effect on the outcome.