"It's been very difficult for him because of the primaries," Dallek said. "He was up against so many people who were so much to the right of him, and he had to protect his flank, because that's where his party is."

An NBC News/Wall Street Journal Poll conducted Nov. 1-3 showed the Democratic Party's brand in better shape than Republicans'. Forty-three percent had a positive view of Democrats compared to 42 percent holding a negative one, while 39 percent viewed Republicans favorably compared to 44 percent who saw them unfavorably. It has been rare for a presidential candidate whose party has the weaker image to prevail in the race for the White House.

Still, Romney appeared to be benefiting from intense Republican sentiment for turning out Obama. A CNN/ORC International poll released Nov. 4 showed a tied contest, with 49 percent of likely voters supporting each candidate, and suggested his backers remain more enamored with the idea of firing Obama than they are of hiring Romney.

Motivations Gap

While 86 percent of Obama's backers said they were voting for him because they genuinely like and agree with him and 12 percent said they were voting against Romney, more than a third of the Republican's supporters -- 37 percent -- said they were supporting him to vote against the president.

The campaign was shaping up to be the costliest in U.S. history, although it wasn't clear whether the billions of dollars spent on television advertising in the most competitive states would amount to a net advantage for either side.

Each campaign also used technology and especially social media in unprecedented ways to influence the contest. Obama, who pioneered the use of social media in presidential politics four years ago when Facebook Inc.'s social network was one-tenth its size and before Twitter was widely used, employed both this year to boost fundraising, recruit volunteers and to try to drive media coverage. Romney's camp used them to mobilize volunteers and boost turnout. On the eve of the election, Obama had 31.8 million Facebook page "likes" to Romney's 12 million.

Hispanic Power

The contest also was testing the potency of Latino voters, the fastest-growing portion of the electorate, and one that is expected to back Obama by a sizable margin.

A poll released yesterday by impreMedia and Latino Decisions found that 73 percent of likely Latino voters planned to vote for the president, compared to 24 percent for Romney.

That would be a greater proportion for Obama than former President Bill Clinton won in his 1996 re-election, when 72 percent of Latino voters backed him. It would also be a significant drop-off in support among Latinos for the Republican; Arizona Senator John McCain, the 2008 nominee, won 31 percent of the Latino vote.