Obama makes calls at a Chicago polling station, congratulates Romney on campaign

"The great thing about these campaigns is after all the TV ads and all the fundraising and all the debates and all the electioneering, it comes down to this, one day,” Obama said, “and these incredible folks who are working so hard, making phone calls, making sure that people go out to vote.”

Obama also took the time Tuesday to congratulate his GOP opponent Mitt Romney on his campaign, noting the hard work of volunteers on both sides of the aisle.

"I want to say to Gov. Romney, congratulations on a spirited campaign," Obama said. "I know that his supporters are just as engaged and just as enthusiastic and working just as hard today.

"We feel confident we've got the votes to win, but it's going to depend ultimately on whether those votes turn out," he continued. "And so I would encourage everybody on all sides just to make sure that you exercise this precious right that we have that people fought so hard for us to have."

After casting his ballot, Romney boarded a plane for Ohio — a key swing state that could decide the election — to visit his campaign office in Cleveland to thank volunteers. He then heads to Pittsburgh to thank volunteers there.