The two candidates have been running neck-and-neck in previous polls of the race. The highly competitive contest in an important presidential swing state is being watched closely by both sides of aisle, as the winner could determine which party has control of the Senate this fall.

The Washington Post poll found that 76 percent of those surveyed said they were "definitely" set to vote for either Kaine or Allen. Seven percent said there was a good chance they could change their minds, and 15 percent said it was unlikely they would change their minds. Three percent said they had no opinion.

The poll was conducted from Sept. 12 to 16 among 934 registered voters and 847 likely voters. It has a margin of error among likely voters of 4 percentage points.

The CBS News/New York Times/Quinnipiac poll was conducted from Sept. 11 and 17 among 1,474 Virginia likely voters with a margin of error of 2.6 percent.

The surveys comes out the same day that Kaine released two new ads.

One ad, "Middle Ground," highlight's Kaine's support of allowing the Bush-era tax rates for incomes above $500,000 to expire. Kaine, the former chairman of the Democratic National Committee, notes that President Obama wants to allow the tax cuts for incomes above $250,000 to expire and Allen wants to extend all the Bush-era tax rates.

The other ad, "Partner," styles Kaine as a bipartisan legislator willing to work with Republicans and Democrats.

"I don't agree with any president all the time but I know that when our nation succeeds, Virginia succeeds," Kaine says in the ad.

Elsewhere, the League of Conservation Voters also announced a $800,000 mail campaign against Allen.