David Axelrod, senior adviser to the Obama campaign, said that the race was close enough that it might take into the early hours of Wednesday morning after election day to get the final results of the presidential race, during an appearance on "Fox News Sunday." 

"I think that some of these races are very close, and so it could extend past midnight into the morning," he said. "I don't think by this time of the morning, we'll still be wondering who the president is," Axelrod said on the 9 a.m. talk show. 

Axelrod also noted that there will be fewer exit polls, which could slow the process of calling the election. "There are fewer exit polls this year, so I think some folks in your business are gonna be a little less bullish about making early forecasts," he said to host Chris Wallace.