Former governors Timothy M. Kaine (D), left, and George Allen (R) are tied at 46 percent apiece among registered voters in the race to succeed retiring Sen. James Webb (D). The pair are shown in Richmond in 2011. (Steve Helber/AP)

The U.S. Senate race in Virginia is deadlocked six months before Election Day, a new Washington Post poll shows, cementing the contest’s status as among the most competitive in the country.

Former governors George Allen (R) and Timothy M. Kaine (D) are tied at 46 percent apiece among registered voters in the race to succeed retiring Sen. James Webb (D), exactly the same place they stood in a Post poll taken a year ago. Both parties believe Virginia will be a key determinant to which side controls the Senate come January.

In the 13 months since Kaine entered the race, the two campaigns have combined to raise and spend millions of dollars, outside groups have poured cash into television ads and Allen has reinforced his position as the Republican front-runner against a handful of challengers. Yet none of those developments has budged the basic narrative — two titans of Virginia politics battling to a draw in a state widely viewed as swing territory, both in the Senate and presidential contests.

Kaine, who served as President Obama’s handpicked Democratic National Committee chairman, might benefit from the fact that Obama holds a seven-point lead over former Massachusetts governor Mitt Romney, the presumed Republican nominee, in Virginia and will drive turnout among liberals and African Americans.

Yet the new poll includes some negative trends for Kaine: Registered voters are now equally divided in their impression of him, with 41 percent apiece viewing the Democrat favorably and unfavorably. A year ago, Kaine’s rating was 2 to 1 positive, at 57 to 28 percent.

Kaine’s decline could be the partial result of negative ads that have aired against him in the state and efforts by Republicans to link him to health-care reform, the stimulus package and other controversial Obama administration policies.

Although his popularity is down across the board, Kaine actually suffered the steepest fall among people planning to support Obama in November. His favorability rating dropped 20 percentage points among that group, even though Kaine has not broken with Obama on any high-profile issues recently. The percentage of non-white respondents viewing Kaine unfavorably climbed 17 points, and his decline in popularity has been pronounced among lower-income voters and those without college degrees.

But the overall portion of registered voters saying they planned to cast their ballot for Kaine hasn’t moved a bit, including among Obama supporters, indicating that backers of the president aren’t planning to abandon the Senate candidate in November.

Stuart Rothenberg, editor of the nonpartisan Rothenberg Political Report, said he had long assumed that for Allen to win, the Republican nominee would need to capture Virginia, while Kaine could potentially scrape out a victory even if Obama lost narrowly. So Rothenberg was taken aback by the fact that Kaine runs behind Obama in the new poll.

“It doesn’t make a lot of sense to me,” Rothenberg said. “It’s a surprise, and, frankly, it’s counterintuitive.”

Arthur Diggs, an African American college professor and Air Force veteran from Virginia Beach, said he planned to vote the straight Democratic ticket this fall. But Diggs said there was no particular reason for him to support Kaine “other than the fact that he leans toward Obama.”

“He’s the lesser of two evils,” Diggs, 63, said. “If it was somebody else [as the Democratic nominee], I would probably vote for them.”

Allen’s rating is also now under 50 percent with voters, though with a smaller slide. His favorability has dipped from 52 to 47 percent in a year, and his unfavorability has inched up from 28 to 31 percent. Allen’s campaign has focused on presenting him as a fiscal conservative who will halt the burgeoning deficits of the Obama administration, while emphasizing Virginia’s strong economic performance during the Republican’s gubernatorial tenure.

But Kaine has sought to remind voters of Allen’s record as a senator, when he voted to raise the debt ceiling and for tax and spending policies that boosted the deficit.

Of more immediate importance, the new poll shows Allen is in a dominant position ahead of his June 12 Republican primary. Among likely primary voters, Allen gets 62 percent, Del. Robert G. Marshall (Prince William) gets 12 percent, former Virginia Tea Party Patriots head Jamie Radtke receives 5 percent and Chesapeake minister E.W. Jackson brings up the rear at 3 percent.

Though all three opponents have accused Allen of being insufficiently conservative, the former governor has no obvious weakness on his right flank. A big majority of self-identified conservatives call him “about right” ideologically, and he takes 68 percent of their votes in the primary.

Allen’s foes have been hurt by their lack of statewide name recognition — 57 percent of all respondents say they didn’t know enough about Marshall to form an impression of him, while 66 percent say the same of Radtke. The four Republicans held a primary debate recently in Roanoke and have two more scheduled this month.

In the general election matchup, Allen and Kaine enjoy massive support from their respective parties, while among independent voters, Kaine gets 46 percent to Allen’s 45 percent.

Kaine leads among moderates, 53 to 38 percent. And the Democrat is up 84 percent to 8 percent among African American voters, a commanding lead that still doesn’t quite match Obama’s 97 to 1 percent advantage over Romney.

Like Obama, Kaine has a solid lead in the suburbs closest to Washington, but the race is far closer in the rapidly growing exurban counties.

The poll shows a clear gender gap: Allen has an eight-point edge among male registered voters, while women lean toward Kaine by seven. Kaine has the advantage among better-educated voters, but the two candidates are running close to even among lower- and upper-income Virginians.

Asked which issues were most important to their choice in the Senate contest, voters most often highlight the economy, health care and the federal budget deficit. Allen leads among those who named the economy, the deficit and taxes as their primary issues. Kaine has the edge among voters most concerned about education. Kaine and Allen run about evenly among those emphasizing health care, an issue that Republicans have sought to use against Kaine.

John Rapp, 66, of Louisa County said he was not overly enamored of either candidate.

“Allen’s kind of hard to figure for me,” said Rapp, a Republican. “I thought he started out pretty well when he ran time before last.”

But he soured on Allen during the 2006 Senate race, when Allen used the word “macaca,” an ethnic slur in some cultures, to refer to an Indian American campaign volunteer working for Webb. Rapp was bothered not so much by Allen’s use of the word — he was willing to chalk it up to a slip of the tongue — as by his shifting explanations for it.

“As a U.S. senator, he needs to be able to think on his feet and handle issues better,” Rapp said.

Yet Rapp, who does research on environmental pollution and occupational disease, is no fan of Kaine. He thought Kaine “fared pretty well as governor,” but he was turned off by his stint as DNC chairman.

Pressed to come down on one side or the other, Rapp said: “If they ran against each other, I would probably vote for Allen.”

Polling director Jon Cohen, polling analyst Scott Clement and staff writers Anita Kumar and Laura Vozzella contributed to this report.