At FiveThirtyEight, Joshua Darr writes
has only one field office in Iowa
According to political science research, Rubio avoids the establishment of a ground game at his peril. Field offices work because they provide a location for the coordination and training that make voter contact valuable. Campaigns that can contact supporters personally to encourage them to vote should make every effort to do so. Knocking on doors can increase turnout by nearly 10 percent, and effective phone calls can encourage an additional 4 percent of voters to head to the polls. Without a field office in an area, candidates will find it much more difficult to translate these tactics into victory.
To be fair, neither canvassing nor phone calls technically require a field office. If a campaign’s main goal is merely to contact as many voters as possible, staff members will often spare themselves the time, effort and cost of training local volunteers by hiring professional callers and recruiting canvassers from out of state. But when campaigns take this shortcut, they often pay the price.
Over the past few presidential elections, field offices have clearly generated higher local turnout. Obama opened 786 field offices in 449 counties in 2012, and each office delivered him approximately an additional 0.3 percent of vote share — or roughly the equivalent of airing 1,000 additional campaign ads. In 2008’s battleground states, Obama earned about 200,000 votes — about 7 percent of his margin of victory in those states — from his network of field offices. These offices accounted for 50 percent of Obama’s margin of victory in Indiana, and they likely made the difference in his win in North Carolina.
These effects seem small, but they make a difference where it matters most. Rick Santorum won the 2012 Iowa caucuses by 0.03 percentage points, or 34 votes out of 121,501. Field offices can be expensive — the estimated cost per vote earned by having a field office is $49.40 — but the earned media and momentum benefits from a victory in Iowa are huge.
Or maybe Rubio figures that he will not win Iowa no matter what, so he is putting his scarce resources elsewhere.