WASHINGTON — Election Day isn’t what it used to be. The presidential winner may be all but known by then, thanks to early voting.

Beginning Friday, residents in North Carolina can submit absentee mail-in ballots — the first of 37 states and the District Columbia to vote by mail or at polling sites before Nov. 8. Four years ago, about 45.6 million people or 35 percent of the electorate attracted by its convenience voted early, and that number is expected to spike in 2016.

That’s where Hillary Clinton’s ground game — at least double the size of Donald Trump’s — could make a difference.

In seven states being targeted by both campaigns — Colorado, Florida, Iowa, Nevada, North Carolina, Arizona and Georgia — early votes are expected to make up 45 to 75 percent or more, based on 2012 numbers. All but Colorado are must-win for Trump.

No votes will be counted until Nov. 8. However, many states report the party affiliation of people who have cast ballots, offering solid clues.

“We could see so many votes banked that it becomes nearly impossible to catch up,” said Michael McDonald, a University of Florida professor and expert in election statistics.

In 2008, Barack Obama made early voting a priority, amassing such big leads with blacks, Hispanics and first-time voters that he pulled out wins in Florida, Iowa, North Carolina and Colorado despite losing the Election Day vote there, according to elections data compiled by The Associated Press. In 2012, he did it again in Florida and Iowa.

Hoping to replicate that success, Clinton is spending millions of dollars on a get-out-the vote effort put into place in the spring. It taps into a detailed database to identify likely voters statewide and down to the neighborhood level, using thousands of employees and sending 50,000-some volunteers door to door to register and educate voters.

Trump, relying heavily on the Republican National Committee, has 133 field offices nationwide and plans to open 24 more over the next two weeks. That’s compared with “hundreds” for Clinton.

Trump’s people have been slow to recruit volunteers in battlegrounds such as Iowa. At this point in 2012, Republican nominee Mitt Romney had a full field staff working intensely with the RNC to identify and reach out to early voters.

RNC officials say they have 1,000 employees and 5,000-plus trained organizers and other volunteers in 11 states assigned to mobilize voters. Heavy focus is on boosting absentee mail-in balloting in Florida, North Carolina, Ohio and Iowa, using the RNC’s own data analytics program.

Acknowledging an uphill battle in early votes, the RNC says its goal will be to keep pace with Democrats and ensure Election Day will decide the outcome after all.