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 (Tim) Michael KaineDem infighting erupts over Supreme Court pick Election Countdown: Latest on the 2018 Senate money race | Red-state Dems feeling the heat over Kavanaugh | Dem doubts about Warren | Ocasio-Cortez to visit Capitol Hill | Why Puerto Ricans in Florida could swing Senate race Green Day's 'American Idiot' climbs UK charts ahead of Trump visit 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.