Bernie Sanders must win New Hampshire. Julian Castro is letting it all ride on Nevada. South Carolina is essential to Cory Booker’s chances.

The 23 candidates chasing the Democratic nomination are piling up events and plowing resources into the four early presidential states, telegraphing which states they’re prioritizing and which ones they’re writing off.

The campaigns are loathe to discuss the primary season map in terms of must-win states or contests they don’t think they can win. But already the outlines of their strategies are showing.

Interviews with nearly two dozen campaign officials, party leaders and grassroots activists in Iowa, New Hampshire, Nevada and South Carolina reveal that staffing decisions, travel schedules and field organizations are starting to have an impact at the county and precinct level.