However, the biggest impact on the end of the campaign was Superstorm Sandy, which blasted the East Coast from Maryland to Connecticut just over a week before Election Day. Obama and Romney canceled campaign events, and the president shifted to full emergency response mode as the storm and its devastation dominated the national focus for much of the final full week of campaigning.
An enduring image of the aftermath was Obama touring the storm damage with New Jersey Gov. Chris Christie, a Republican and top surrogate for Romney. The image and Christie's praise for Obama's handling of the crisis undermined a major Romney argument that the president valued personal gain over the good of the nation.
Final polls indicated Obama inching ahead nationally and in most of the battleground states, though the race remained too close to call.
"The hurricane is what broke Romney's momentum," Haley Barbour, the former Republican governor of Mississippi, told CNN on Sunday.
On the ground, record numbers of voters cast early ballots as both sides boasted of ramped-up organizations to identify and contact supporters. At the same time, Democrats complained that Republican-led state governments passed tighter voter registration laws in an effort to suppress minority turnout.
Overall, the total cost of the election for president and Congress could top a record-breaking $6 billion, according to the nonpartisan Center for Responsive Politics. The figure covers spending from January 2011 through whatever totals emerge after Tuesday's election.
Outside groups accounted for the biggest boost in spending, with independent organizations dropping more than $970 million. The increase was largely related to the 2010 U.S. Supreme Court ruling that paved the way for super PACs to raise and spend unlimited amounts of money as long as they did not coordinate with the campaigns.