Former Virginia Gov. Tim Kaine (D) leads former Sen. George Allen (R-Va.) by 6 percentage points, according to a new poll from NBC News.

The poll has Kaine leading Allen by 49 percent to 43, his largest lead in any survey for months, although NBC's last poll of the race, in early March, had him up 9 points while others showed it much closer. The two are locked in a tight battle for retiring Sen. Jim Webb's (D-Va.) open seat.

The same poll had President Obama leading Mitt Romney by 48 percent to 44. Virginia is a crucial swing state for both the presidential race and control of the Senate, and since Kaine and Allen are so well-known there it is unlikely to see much movement in the polls without a major event between now and Election Day.

Kaine will have some big help Thursday: Vice President Joe Biden will head to northern Virginia to headline a fundraiser for him.

The poll was conducted from May 17-20 and has a margin of error of plus or minus 3 percent.

This post was updated at 11:50 a.m.