Updated 2 p.m. | Republican Rep. Frank R. Wolf will not seek an 18th term in Congress, according to a statement from his office.
"I have decided not to seek re-election to the U.S. Congress in 2014," Wolf, the dean of Virginia's congressional delegation, said on Tuesday. "It has been an honor to serve the people of northern Virginia and the Shenandoah Valley."
"I thank my constituents for giving me the privilege of representing them in Congress for 34 years," he added.
Wolf's decision puts into play a Northern Virginia seat that was only safe based on the strength of his incumbency. Democrats are almost sure to go after it. Mitt Romney narrowly carried the district, with 50 percent of the vote to President Barack Obama's 49 percent, in 2012.
Still, a long list of ambitious Republicans will likely consider running for the open seat. Republicans immediately named state Del. Barbara Comstock, a former Wolf aide, as a top potential candidate.
Former Rep. Artur Davis, D-Ala., who switched to the GOP, told CQ Roll Call in February that he would be interested in running should Wolf retire. In response to a Tuesday inquiry from CQ Roll Call, Davis did not rule himself out of the race.
"I will monitor the field that develops in the next several weeks in the hope that a responsible center-right candidate will emerge, one who gives Republicans a chance to keep this district and who will represent the best of the Virginia Republican Party," Davis said in a statement.
Attorneys Richard Bolger and John Foust are already running for the Democratic nomination.
The 10th district encompasses much of exurban Virginia outside Washington, D.C. It stretches east from the West Virginia border, with tentacles to the north reaching deep into McLean along the Potomac River and to the south to the Occoquan along Interstate 95.
Wolf is the seventh House Republican this Congress to announce his retirement.
Update 2:30 pm: State Sen. Jill Holtzman Vogel, who was initially mentioned as a possible Republican candidate, told the Washington Post that she would not run for the seat.