In 2007, Barack Obama’s campaign for the Democratic nomination opened one of its 37 Iowa field offices in the small town of Elkader, population 1,300. No Democrat since has set up shop there. The same is true of Oelwein (population 6,100), where Obama himself stopped by the office to chat with voters in October 2007, and Algona (population 5,300), where singer Carole King made an appearance.

Obama’s ground game in the 2008 Iowa caucuses was particularly comprehensive— he opened local offices in small towns and rural counties across the state, in addition to the bigger cities — and essential to his eventual victory. Field offices can be crucial in the caucuses: They act as points of coordination for get-out-the-vote activities such as door-knocking and phone calls, which are proven ways to turn out voters.

But the 2020 campaigns, despite some robust field organizations, are not following Obama’s lead in Iowa. Their field office footprint is much smaller: Warren and Biden currently have 24 offices each, the most of any campaign, according to my data. And there are 10 counties in which Obama had an office, but the four front-runners in Iowa — Mayor Pete Buttigieg of South Bend, Indiana, former Vice President Joe Biden, Sen. Bernie Sanders and Sen. Elizabeth Warren — do not. Based purely on the number and location of field offices, there is little daylight between the top four candidates, and none appear to have a distinctive field strategy. As you can see in the map below, the top campaigns have roughly equal numbers of offices in essentially the same locations.

So what can we say about the 2020 candidates’ strategy in Iowa so far?

First, let’s look at the counties that today’s candidates have in common with Obama in ‘08. In total, there are 13 counties where Obama had an office in 2007-08 and all four front-runners have an office now. These “Obama and 2020” counties include the nine most populous counties in the state, among them Polk (population 487,200 and home to Des Moines) and Story (population 98,100 and home to Ames, where Iowa State University is located), and lean Democratic relative to the state. Hillary Clinton won 45.6 percent of their votes in the 2016 general election, which was 4 points higher than her overall performance in Iowa. And in 2008, these counties voted even more solidly Democratic, averaging 57.4 percent for Obama in the general election.

Given that there are more precincts (and therefore more delegates) in more populous areas, the logic for investing in cities like Iowa City, Dubuque, Cedar Rapids and Waterloo is clear, and something Obama did in 2008, too. However, in the caucuses, delegates are apportioned at the precinct level, not the state-wide vote totals. This means that campaigns cannot simply “run up the score” in populous areas while abandoning rural precincts: They must cast a wider net to increase the number of opportunities to win delegates, which is what matters.

But where to expand? Is there an argument for investing in the areas that Obama avoided in 2008 and where today’s candidates have also not opened offices? Probably not. It’s not easy to knock doors in areas where the houses are far apart, and these 63 counties are very small and rural. The average population is around 12,700, or about one-tenth the average size of the counties that hosted offices for both Obama and all 2020 front-runners, which means the pool of likely caucusgoers is low. These counties that have never had a Democratic field office have also shifted, on average, 17.9 points away from Democrats between 2016 and 2008, a much larger change than the 11.8 percent shift away from Democrats in counties that hosted offices for Obama and the 2020 candidates. The cost of opening and staffing offices in these counties probably exceeds the potential benefits of overperforming in these areas.

On the other hand, there is ample opportunity to reach voters in the 10 Obama-only counties, where today’s campaigns have so far steered clear. These counties’ average population is more than double that of the counties that have never had an office (26,350), and they were nearly 8 points friendlier to Clinton in 2016 (she won 36.6 percent of the vote in Obama-only counties, compared to 28.8 percent in counties with no offices). In 2008, those 10 counties even voted for Obama in the general election (54.5 percent of the vote in these counties) — much closer to the counties with Obama and 2020 offices (57.4 percent) than the officeless counties (46.7 percent). But today’s candidates are leaving them without offices, despite relatively higher populations and potentially friendly voters.

A caveat is necessary here, though: field offices are not the only sites of organizing activities, and today’s campaigns may be doing more with less office space. Libraries, coffee shops and breweries frequently host campaign events in areas with and without offices. Warren’s campaign, for example, conducts frequent volunteer events in “Obama-only” towns like Maquoketa and Algona, while the Buttigieg campaign holds regular canvasses in Waverly. Advances in technology may be changing the role field offices play by making it easier to connect staffers with potential volunteers.

Simply put, the candidates this cycle are not anywhere close to approaching Obama’s 37 field offices, but it’s not entirely clear whether that’s due to gains in efficiency, changes in strategy or lower effort. There is still plenty of room for the top 2020 candidates in Iowa to grow if they decide to invest more in field operations, though they are running out of time. Given how closely grouped the top four candidates are, even a small boost from additional field investment could put one of them over the top in the caucuses on Feb. 3.