A poll released Wednesday by Quinnipiac University also found the race close, with Kaine leading 48-46 percent.

"Virginia's U.S. Senate has been a dead heat since it began," Peter A. Brown, assistant director of the Quinnipiac University Polling Institute, in a statement. "It's pretty clear that whether George Allen or Tim KaineTimothy Michael KaineAuthorizing military force is necessary, but insufficient Week ahead: Crunch time for defense bill’s cyber reforms | Equifax under scrutiny Insurer Anthem to cover bare ObamaCare counties in Virginia MORE becomes the Old Dominion's next senator, it almost certainly will be by a razor-thin margin."

The same Rasmussen poll found President Obama with a 48-46 percent advantage in Virginia over presumptive Republican nominee Mitt Romney. The poll carried a margin of error of 4.5 percent.