In the race's final days, the campaign that does the better job choosing where to send their candidate may be the ultimate winner.

At the Obama rally in Dayton on Tuesday, buses were lined up to take voters to local polling places as soon as the president left the stage. Romney aides kept a careful watch on the polling places in the area to see if there was a noticeable increase in activity. (They naturally say there wasn’t as much as they would have expected; the Obama team claims the early voting in that area has far outstripped the totals from 2008.) If the Romney team did detect a lot of activity after the rally, they could redirect their efforts. They’d make more phone calls into those neighborhoods and surrounding suburbs, they’d send volunteers to knock on more doors, or they’d send a surrogate. If it were serious, they might mark the area with a big red X for a future visit from the candidate himself.

How closely are the campaigns watching these early vote totals? The Romney campaign saw an uptick in votes in Belmont, an Ohio Democratic stronghold,  and worried party loyalists were rallying around Obama. They launched an investigation. Using the list the Ohio secretary of state releases each day of early voters, they called some of those who had voted and polled them. It turns out, according to a Republican source, that those voters were coming out to vote against the president and his coal policies.

Finally, when the candidate comes to town it offers an opportunity to broadcast a message to undecided voters who might never attend a rally. “Until he’s commander in chief, he’s persuader in chief,” said one of Romney’s top Ohio lieutenants about the candidate’s visit to the state. Romney’s job is to drive a message in local media that gets through to undecided voters. It is calibrated by looking at the state’s most recent polling numbers so that the message can be aimed at white women or Hispanic voters. “He needs to sound like their neighbor, too,” says one local Obama staffer of the targeted messages fed to the president. “That’s what builds up trust.”

It’s also a chance to push for votes, as Romney did in Cincinnati on Thursday. “I need you to find someone else who might be willing to vote for the other side,” he said. “Go out there and find some people, bring them to the polls. For someone who doesn’t have a ride, get them to the polls.”

As the days dwindle, the campaigns will be forced to make brutal decisions about where they should deploy their candidate. What states are in the greatest need of a visit? Based on last-minute polling data, which portions of a state are more important than others?  Could a presidential visit in some cases actually distract the army of volunteers from their last weekend duties of going door-to-door by pulling them to the rally and away from the neighborhoods? Soon some states will start to feel orphaned. Each campaign has enough money to keep buying television ads until the final day. The real test will be deciding whether the candidate comes to town.