Democrat Tim Kaine continues to lead Republican George Allen in Virginia's hotly contested U.S. Senate race, a new poll shows.

Kaine had 49 percent of the vote to Allen's 44 percent, extending the lead Kaine established three weeks ago after months of deadlock between the two former governors, according to an NBC News/Wall Street Journal/Marist poll of likely voters released Wednesday.

"We've always believed that once we start to engage on the air that our message would start to resonate, and we are confident that it's happening," said Mo Elleithee, a senior adviser to Kaine. "This race is still a margin-of-error race, and we're going to treat it as such until the end."

Kaine's momentum is coming from the Democratic base, particularly nonwhite voters, who until recently were strongly in President Obama's camp but were less enthusiastic about Kaine. In September, while Obama's support among nonwhite voters was 77 percent, Kaine's hovered around 67 percent. Nearly eight in 10 minority voters now back Kaine, very close to the 82 percent backing Obama, the poll shows.

Both Kaine and Obama have enjoyed a significant bump among voters between the ages of 18 and 29 as well.

The results are more closely in line with what many expected: a Senate race that mirrors the presidential contest in battleground Virginia. Kaine's lead over Allen is actually outpacing Obama's 2 percentage-point advantage against Republican challenger Mitt Romney, thanks to independent voters who still prefer Romney but now give Kaine the edge over Allen.

"The president is slightly stronger in Virginia, and it has helped Kaine down the ballot," said Geoffrey Skelley, political analyst at the University of Virginia Center for Politics. "We've always been a little suspicious that there might be a few Romney-Kaine voters out there, and maybe that's part of this as well."

The new poll comes after Kaine spent a week fending off criticism of a debate comment in which he said he would consider a minimum federal income tax for all.

Allen's inability to dent Kaine's standing in the aftermath of the tax comment may indicate greater problems for Allen in closing the current gap, Skelly said.

"It's the one noticeable error that the candidates have made so far," he said.

One thing likely hurting Allen is the barrage of ads Obama is airing in Virginia about Romney's claim that 47 percent of Americans are dependent on government and don't pay taxes.

Allen said Tuesday the impact of Romney's remarks on his race is "not something I know one way or the other."

"I have my own point of view," Allen said, "and we're running on our Blueprint for America's Comeback."