Central to the Biden campaign’s theory is the belief that, after the Feb. 29 primary in South Carolina, the now-sprawling Democratic field would be narrowed to just two candidates. And one of them — Biden — would be far better positioned to amass delegates on a primary date that offers a windfall of roughly 1,300.

By contrast, in the four early-state contests only 155 delegates are up for grabs.

“If history is any guide, this will likely be a two-person race coming out of South Carolina, and whomever emerges from Super Tuesday with a significant delegate lead will be extremely difficult to catch,” a senior Biden official said.

Under Democratic delegate selection rules, some congressional districts are allocated more delegates than others. For months, the campaign has zeroed in on the most delegate-rich congressional districts in Super Tuesday states like Texas, North Carolina, California and Alabama and attempted to assemble slates of supporters specific to those districts.