As Super Tuesday votes are counted, the biggest question will be how many delegates each candidate won.
We probably won’t know the answer for some time.
Let’s walk through the night. The first polls close at 7 p.m. Eastern time in Vermont and Virginia, and we’ll start getting results soon afterward. We may know quickly who won those two states.
We should also learn relatively early which candidates won the three other states in the East: Maine, Massachusetts and North Carolina.
Polls will close
Here’s a cheat sheet for the night
Mr. Biden should do well in Virginia, North Carolina and Alabama, given his strong support among black voters, who make up a large share of the Democratic primary electorate in those states. Vermont and Maine ought to be friendly territory for Mr. Sanders.
If surprises happen — Mr. Sanders surging in the South, Mr. Biden doing better than expected in New England — it could alter expectations of how the night will go. Also watch to see if Senator Elizabeth Warren of Massachusetts, who was behind in the polls, starts hitting the 15 percent threshold in many places and picking up delegates.
We’ll also finally learn how much support former Mayor Michael R. Bloomberg has among voters. Tuesday is his first time on any ballot outside of New York City.
Because of Mr. Sanders’s strength in California — he has the largest team, has raised the most money and is the most popular among Latino voters — he is widely expected to win the most delegates on Super Tuesday. The issue is how big a lead he will have over his closest competitor — and how many rivals will reach the 15 percent threshold.
The delegate scenarios to watch for
Heading into Super Tuesday, Mr. Sanders led with 60 delegates to Mr. Biden’s 53.
There are 1,357 delegates at stake in Tuesday’s vote. If Mr. Sanders emerges with a lead of 250 delegates or more, he will be in great shape this spring to collect the outright majority of delegates required to clinch the Democratic nomination.
But if his lead is narrower, say 100 delegates, and Mr. Biden does well in the South and Texas, he will have a real shot at catching Mr. Sanders in the delegate race, given the makeup of the states to come. That could mean a long, bitter two-way battle.
Then there is a third possible scenario: If Ms. Warren and Mr. Bloomberg make the 15 percent threshold in more places than expected, they could limit the number of delegates that go to Mr. Sanders and Mr. Biden.
That would give political oxygen and momentum to two candidates who desperately need it and put the party on the path to a four-way fight to the July convention in Milwaukee.