10 of the closest presidential elections in United States history

The latest CNN/ORC International survey released Sunday shows President Barack Obama and Republican challenger Mitt Romney tied in the race for the White House, 49 percent to 49 percent. During Tuesday's election, both candidates will be aiming to reach the required 270 electoral college votes.

Although expectations suggest the race between Romney and Obama will be close, the United States has faced tight elections before. Here's a look at 10 of the closest presidential elections in American history.