Washington: Michigan, Washington, Missouri, Mississippi and Idaho hold Democratic primaries on Tuesday, while North Dakota has a caucus. There are 352 delegates up for grabs. A candidate needs 1,991 delegates to win the Democratic presidential nomination.
That makes for only the fourth-largest delegate night on the primary calendar. But the intricate arithmetic of how delegates are won under Democrats' rules makes it possible for a candidate to reap a bigger haul of delegates with a smaller margin of victory on this Tuesday than on any other night.
For Bernie Sanders, it's an opportunity to catch up to Joe Biden, who enters the day ahead by 96 delegates. For Biden, it's a chance to open up what could become an insurmountable lead.
Most delegates awarded on Tuesday — 65% — will be won based on how the candidates perform in individual congressional districts. Think of each district as holding a bucket of delegates. There are also two buckets of delegates in each state awarded based on the overall statewide vote.
On Tuesday, that makes for 51 buckets of delegates across the six states. A candidate needs to win at least 15% of the overall vote in a bucket to be “viable” — or to qualify to win delegates. (That 15% threshold means it's all but assured that only Biden and Sanders win any delegates from this point forward)
Read: Biden hopes to continue momentum in key Michigan primary
Party rules say each viable candidate wins a proportion of the delegates in each bucket based on his share of the votes cast for the viable candidates in that bucket.
Second, buckets that have an odd number of delegates are impossible to split evenly, meaning either Sanders or Biden is guaranteed to win at least one more than the other.
Nearly two-thirds of the 352 delegates at stake on Tuesday are in buckets with an odd number of delegates — more than on any other night with more than one primary.
Biden or Sanders will need to win far more than 50% of the vote in a bucket to win more delegates than his rival. From a bucket holding six delegates, a candidate needs more than 58.3% to win four delegates. In a district with eight delegates, the leader needs 56.3% to get five.
Put another way, a candidate could keep coming in second in the overall vote, but so long as he keeps the race relatively close, he'll still end up with the same number of delegates in an “even” bucket as the candidate who finishes first.
And that means whoever does best on Tuesday, and next week when Arizona, Florida, Ohio and Illinois get their turn, could end up with a delegate lead that can't be beat.
(With inputs from AP)
