Political operatives call it the ground game advantage: how well the parties get out the vote. It can tip the scales just one or two points in favour of either candidate. With some of the crucial battleground states, such as North Carolina and Florida, still too close to call, it could be a significant, if not deciding, factor in tonight's U.S. election.

And on that score, it would seem that Democratic candidate Hillary Clinton has an advantage over Republican candidate Donald Trump.

"Clinton very clearly has a larger and more extensive field operation than Trump and the [Republican National Committee]," said Joshua Darr, assistant professor of political communication at the Manship School of Mass Communication at Louisiana State University.

Darr has noted, for example, that Clinton has twice as many field offices as Trump, and that her organization dominates Trump's in every battleground state.

"The scarceness of Trump's offices in several of his must-win states, and their unclear focus on his candidacy, cast real doubts on the Republican nominee's ability to get out the vote," Darr wrote recently on statistical analytics website FiveThirtyEight.com.

Democratic strategist Brad Bannon is emphatic that there really is no comparison between the two campaigns in terms of a ground game network. Unlike Trump's team, the Clinton campaign, he said, has "thousands and thousands" of people mobilized all across the country.

Trump and his campaign have all but relinquished control of the ground game to the Republican National Committee and local and state party officials. (Scott Sonner/Associated Press)

"And I think that's worth a point or two. In some states, it will probably make the difference," Bannon said. "I think the Clinton ground advantage could make or break those states."

The campaigns each try to identify their candidate's supporters and organize ways to get those voters to the polls on election day. That includes sending volunteers to their doors, calling voters to remind them to vote, making sure they know where to vote and supplying rides to the polls.

'Have not matched Clinton's efforts'

But there's a big difference in how the candidates are running these operations. The Clinton campaign is in charge of its ground game but has worked in tandem with the Democratic National Committee to co-ordinate field efforts. However, Trump and his campaign have all but relinquished control of the ground game to the RNC and state party officials.

"The RNC has got that under control, and they have not matched Clinton's efforts, and it's unclear if they will be the messengers that [Trump] wants them to be on election day because his campaign hasn't exactly contributed a lot on that front," Darr said.

The problem for Trump is that in some states, the RNC has decided to focus its resources more on getting Republican senators elected in tight races than on the presidential candidate.

I think it's somewhat odd that Trump has relinquished quite a bit more control to the RNC than other candidates have. - Joshua Darr , assistant professor of political communication, Louisiana State University

Not only does this steer the focus away from electing Trump, it can have the effect of mobilizing ticket splitters — Republicans who will vote for their party's senator but not its presidential nominee.

"I think it's somewhat odd that Trump has relinquished quite a bit more control to the RNC than other candidates have," Darr said.

Trump, early in his campaign, made a conscious choice not to invest in these ground game resources, said Republican strategist Ron Bonjean. Instead, Trump hoped that communicating to voters through numerous rallies and press conferences would draw them to the polls.

"We'll see on election day whether that was a mistake," Bonjean said. "It would have been wiser to use every tool in his arsenal to get voters out there to the polls. But if he wins, he'll prove himself correct."

In Florida, a crucial state for Trump, the Democrats' get-out-the-vote campaign might already be producing important electoral gains. Early voting shows that Hispanic voters, many of whom may oppose Trump because of his controversial comments about Mexicans and his position on illegal immigration, have already voted in record numbers.

'Where the rubber meets the road'

"The ground game is where the rubber meets the road in Florida," said University of Florida political science professor Daniel Smith.

While Clinton's ground game in Florida might not quite match that of Barack Obama's in 2012, Smith said Clinton's campaign has offices across the state, with thousands of volunteers as well as paid staff. Trump, meanwhile, must rely on the Republican Party in Florida, a formidable operation in the state, said Smith.

The Clinton campaign runs its ground game but has worked in tandem with the Democratic National Committee to co-ordinate field efforts. (Paul Vernon/Associated Press)

"But how many of those establishment Republicans who are part of the party are really going to be working on behalf of Donald Trump?" asked Smith. "That's one of the big questions."

Bonjean said while Clinton certainly has the strong ground game advantage across the country, Trump has the enthusiasm factor.

"That's why the [Clinton campaign] has put out a strong get-out-the vote network," he said. "Whether or not that will help on election day is still up in the air, but you would rather have a valuable network than not at all."