Update, 6:08 p.m.: Washington Post Polling Director Jon Cohen warns to be cautious of the Senate race numbers from this Roanoke College poll. Results were adjusted only for gender, and the resulting sample is not representative of Virginia’s racial composition, its age structure or regional population densities. Each of these factors is related to partisan preferences.

Original post: A new poll shows ex-Sen. George Allen (R) leading former Gov. Timothy M. Kaine (D) by double-digits in their race to succeed retiring Sen. James Webb (D), with a quarter of Virginians still undecided 19 months from Election Day.

The Roanoke College poll gave Allen a 45 percent to 32 percent lead over Kaine, with 23 percent unsure. The survey of likely voters was released Thursday, two days after Kaine officially announced he was entering the race, but it was conducted from March 17 through March 30. The poll has a margin of error of plus or minus 4.7 percent.

“Among the battleground groups, Kaine led among political moderates (41%-34%), while Allen led among Independent voters (40%-35%),” according to a memo accompanying the poll. “Not surprisingly, Allen led among Republicans (78%-4%) and conservatives (68%-10%) while Kaine led among Democrats (79%-12%) and liberals (83%-10%). Allen’s lead could be attributed to the large number of conservatives in Virginia, a finding that closely matches the December, 2010 Roanoke College Poll.”

The survey also found that 49 percent of Virginians said they believed things in the state are going “in the right direction,” and that Gov. Robert Mc­Don­nell (R) had an approval rating of 66 percent — a nine-point improvement since December.

The Roanoke College poll differed significantly from one released in early March that was conducted by Public Policy Polling, a Democratic-leaning firm that uses autodial technology rather than live interviews. That survey found Kaine and Allen tied among registered voters at 47 percent each.

Before Kaine and Allen can square off ,each must win his party’s nomination. Allen faces a potentially crowded primary that includes tea party leader Jamie Radtke. Kaine faces no declared opposition, though Rep. Bobby Scott (D) hasn’t ruled out a bid.