Back in late August, PBS reported a huge disparity in the number of campaign offices held by Donald Trump and Hillary Clinton in key swing states. At the time, across 15 key states, Clinton had 291 offices to Trump's 88. The chart below shows Clinton's overwhelming office advantage in nearly all these states.

Since then, the Republican National Committee and the Trump campaign have stepped up their ground game operations, especially in places like Florida, where Trump now has around 27 offices. The campaign is also reported to have greatly expanded its presence in New Hampshire, Pennsylvania, and Ohio, although exact office counts from both campaigns are not available.

There is no question that the Trump campaign has been slow to develop a ground game operation, especially in key states. This basic campaign oversight has been called "political malpractice" by some observers.

But is it?

There is some uncertainty about how important field offices are in turning out voters and affecting vote share, but systematic studies on this question have demonstrated a modest positive relationship between field offices and candidate vote share. Studies of recent presidential elections have found that candidates do better — by roughly half a percentage point to a point — in counties where they place field offices than in those where they don't. Another study has shown that people living closer to field offices are more likely to turn out to vote.

These analyses all go to the campaigns' respective "ground games," a term that usually refers to organized local efforts to get voters to turn out on Election Day, usually in the form of phone banking and door knocking. This is typically performed by, and even coordinated by, volunteer labor, and thus we do not have great systematic data from past campaigns as to how their ground games were run.

Clinton appears to be running a similar sort of ground game to the one assembled by the Obama campaigns in 2008 and 2012, with hundreds of offices coordinating millions of volunteers using frequently updated voter contact lists. The Trump campaign has been slow to invest in such activities, but appears to be ramping up in the final month of the campaign.

A strong ground game means a candidate is well-organized, and well-funded, with many enthusiastic volunteers. To some extent, ground game is simply a proxy for the sophistication and overall support a campaign enjoys.

In addition to its direct impact on voters, the ground game is indicative of other aspects of a presidential campaign. For one thing, opening and maintaining hundreds of field offices is expensive in terms of time, labor, and money. A strong ground game means a candidate is well-organized and well-funded, with many enthusiastic volunteers. To some extent, ground game is simply a proxy for the sophistication and overall support a campaign enjoys.

Second, ground game capacity is important because the political science literature shows us that voters are more likely to turn out when they are asked to, and when they perceive social pressure to vote. This means that canvassing, door-to-door interaction with voters, nitty-gritty assistance with voter registration, transportation to polls, and simple encouragement by those around you to go and vote can have a positive effect on one's probability of turning out to vote.

Now, we shouldn't overstate the importance of a ground game. In 2008 and 2012, the Democratic candidate won the White House, and the Democratic candidate had about a 3-to-1 advantage in campaign offices over his Republican opponents. Curiously, in the 2014 Colorado US Senate race, Democratic incumbent Mark Udall also maintained a 3-to-1 field office advantage over Republican challenger Cory Gardner, but Udall lost.

According to the recent PBS report, Clinton has about 3.3 offices for every one that Trump has in swing states — a slightly greater advantage than usual but still pretty close to the typical ratio. At least in recent years, Democrats simply place greater emphasis on maintaining field offices than Republicans do, and it's not obvious that this advantage determines the winner.

To the extent that campaign offices and volunteers indicate something about the level of enthusiasm a candidate enjoys, then field office comparisons may be one of several indicators that help us understand the public winds in an election. It's unlikely that an immature or underdeveloped ground operation will actually sink a candidate, but we don't have examples of that operating in isolation. If you have a bad ground game, chances are other aspects of your campaign are lousy too.

But this is another area in which Hillary Clinton is running a conventional presidential campaign and Donald Trump just isn't. If past studies are any guide, Trump's lack of ground game investment could end up costing him a point or so on Election Day. But whether that will make the difference remains to be seen.