A retired Air Force general is running to unseat Rep. Frank Wolf (R-Va.), giving Democrats an early contender in a district where they have had difficulty competing in recent election cycles.

Retired Gen. John Douglass — who held national security posts in both the Reagan and Clinton administrations as well as NATO — said Tuesday that he would run for the Democratic nomination because “it’s time to have an independent voice” in Virginia’s 10th district.

“At this critical time, we need someone who has a proven record of standing up, taking on the tough fights, and winning them,” Douglass said in a statement released by his campaign. “I’ve served this nation for over three decades and have the proven-leadership needed to tackle the complex challenges we face this century.”

Wolf has won reelection with ease in recent years despite concerted Democratic efforts to beat him. President Obama won the 10th district — which stretches from McLean across Loudoun county to the West Virginia border — by 7 percentage points in 2008. Timothy M. Kaine also won the district in his 2005 race for governor, and James Webb (D) and Mark Warner (D) won it in their 2006 and 2008 Senate victories, respectively.

But Wolf beat another Air Force veteran — retired Col. Jeffery R. Barnett (D) — by 28 points in 2010. And he beat Judy Feder (D), who had organizational and financial support from national Democrats, by 16 points in 2006 and 20 points in 2008.

Democrats are hopeful that 2012 might be different, partly because of Wolf’s votes in favor of bills to cut government spending in a district that is packed with federal workers and installations.

But the 10th district — which has seen huge population growth over the last decade -- could soon be more friendly to Republicans. The Virginia General Assembly has yet to agree on new congressional district lines, but the plan that is viewed as likeliest to pass would shrink the 10th geographically by shedding some Democratic-leaning areas to Reps. James P. Moran Jr. (D) and Gerald Connolly (D).