THE 17 people who control the Republican Party in Northern Virginia’s 10th Congressional District are a cabal of insiders; they make the rules by which the party nominates congressional candidates. In that role, their guiding light appears to be Boss Tweed, Tammany Hall’s major-domo, who said, “As long as I count the votes, what are you going to do about it?”

At the moment, according to GOP sources, the strong likelihood is that the Gang of 17, dominated by conservatives, will opt for a convention next spring, not a primary, to choose a candidate to succeed Rep. Frank R. Wolf, the Republican incumbent who is retiring. A convention would be insular, exclusive and sparsely attended; at a stretch, it might draw 5,000 party activists, mostly hard-core conservatives, who don’t mind sitting through six hours of speeches on a Saturday before casting their votes. A primary, open to all, could attract a more mainstream pool of 25,000 or 30,000 voters.

Despite their limited attendance and poor record of picking winning candidates, conventions have been the nominating method of choice in recent years for Virginia’s GOP. (Democrats have stuck with primaries.) To the conservative clique that has captured the party’s ruling councils, the fact that conventions tend to produce losers — just look at the Republican slate for governor, lieutenant governor and attorney general that was swept in November — seems beside the point. Only ideological purity matters; moderates need not apply.

The 10th District sits atop Virginia like a crown, stretching across Loudoun, Fairfax, Prince William, Fauquier, Clarke and Frederick counties. It is Virginia’s tippiest swing district. Mitt Romney, a Republican, won the district by a single percentage point last year. Sen. Timothy M. Kaine (D) won it by a similar margin the same year. Mr. Wolf has survived in office for 17 terms as a moderate, downplaying social issues like abortion and gun control.

Evenly divided among Republicans, Democrats and independents, the 10th District seems a particularly bad place to engineer the selection of a hard-line conservative candidate. Yet that’s exactly what the local party bosses have in mind, sources tell us. We don’t much care that Virginia’s GOP is strategically obtuse or that its approach has produced an all-Democratic lineup of statewide officeholders for the first time in more than 40 years. We do care about democratic principles.

Conventions, which systematically exclude thousands of otherwise willing voters, are un-democratic. They make no provision for absentee voting, which means that active-duty military members serving overseas or away from home cannot take part. They are generally held on Saturdays, which makes participation difficult for owners of stores and other small businesses, not to mention soccer moms and dads. Ordinary Virginians who would like to exercise their prerogative as citizens but cannot spare an entire day sitting in a high school gym are out of luck.

One prominent Republican took himself out of the running this month. Artur Davis, formerly a Democratic congressman in Alabama, had moved to Virginia with an eye to running to succeed Mr. Wolf. He saw which way the wind was blowing. “The process of competing for a partisan nomination wouldn’t exactly allow me to run a campaign focused on building common ground,” he said. It’s hard to blame him. In Virginia’s modern Republican Party, the deck is stacked against moderates.