President Barack Obama was spending Election Day Tuesday in his home state of Illinois, reportedly playing basketball and then watching the returns. Republican challenger Mitt Romney was holding two final campaign stops in Ohio and Pennsylvania, before retiring to his campaign headquarters in Boston in the evening to watch the results come in.

With voting in full swing, long lines were reported at polling stations across the country. The Obama campaign was betting on its well-run organization turning out the vote, especially among younger Americans; the Romney camp was adamant that the momentum was with its candidate.

With campaigning largely over, the final polls offered a worrying snapshot for Romney.

RealClearPolitics’s average of polls showed Obama ticking up in the polls nationwide by a slight 0.7% margin, while the New York Times election statistics blog FiveThirtyEight showed a more comfortable lead for the president, at some 2.5%.

Polls have been contested by both sides in this remarkably close race. The winner, the campaigns believe, will be decided by turnout and enthusiasm, not national polling. It is there, Republicans claim, that Mitt Romney will have the decisive advantage.

US media offered a colorful symbol of the divided country in election results from the ten-resident hamlet of Dixville Notch, New Hampshire, where voters were evenly split, five to five.

The three national polls published Monday showed the same result throughout America, with a Politico/GWU/Battleground poll showing the candidates at an even 47%, a Rasmussen poll giving Romney a one-point lead (49-48), and an IBD/TIPP poll showing Obama with a one-point lead (50-49).

One scenario has Mitt Romney winning the popular vote, which he has led in recent days, but due to the distribution of Electoral College votes among the states, losing the White House. This scenario is not implausible. FiveThirtyEight puts a chance of that happening at a remarkably high 5.3%. It would mark a reverse of the 2000 election, where Democratic candidate Al Gore won the national popular vote but lost the Electoral College.

Both parties will be watching exit polls through the night, though exit polls may not give an accurate picture of the winner in such a close race. In the 2011 recall vote for Wisconsin Governor Scott Walker, Walker lost in the exit polls by 1 percentage point, but ended up winning the actual vote tally by 7 points.

The most expensive campaign in history

With a whopping $6 billion spent on political advertising in this election cycle, the 2012 campaign is also the most expensive in US history, with many hundreds of millions in political advertising coming from unknown sources.

This year’s race is the first presidential election after the 2010 Supreme Court Citizens United decision, which led to the creation of “super PACs,” groups that can receive an unlimited amount in donations and spend it on political messaging.

“In the new campaign finance landscape post-Citizens United, we’re seeing historic spending levels spurred by outside groups dominated by a small number of individuals and organizations making exceptional contributions,” according to Sheila Krumholz, executive director of the Center for Responsive Politics.

According to a report released by the center last week, each presidential campaign, together with its party committees, spent some $1 billion on the race, while some $550 million were spent by outside groups on the presidential campaign alone. Approximately $1.8 billion were spent on Congressional races, all told.

More than $200 million were spent by the candidates themselves on their Congressional races.

According to the report, some $970 million were spent by outside groups, $540 million by super PACs, who must report their donors, and $351 million by other nonprofits who do not have to report contributors.

Money isn’t everything, there’s also Facebook

As the campaign winds down, the power of social media in politics has been reaffirmed.

According to a Pew Center study conducted November 1-4 and released today, fully 30% of registered voters told Pew they were encouraged to vote for either Obama or Romney by family or friends through the social media sites Facebook and Twitter. One in five respondents said they had done the encouraging.

The figures show a huge age gap that suggests the role of social media and the influence of friends and family on voting may only increase. Among those aged 18-29, 45% were urged to vote through social media, with 40% of those aged 30-49 saying the same. Between ages 50 and 64, the figure drops to a still considerable 27%. Even over 65, 11% said they have been encouraged to vote through social media.

Fully 29% of those aged 18-49 had announced their vote on social media after the fact.

Neither side has an advantage on social media messaging, the study discovered, with 25% reporting they had been urged to vote for Obama, and an identical 25% saying the same for Romney.