While each internal faction in the House sets its own rules for admission, the Blue Dog Coalition may have just established itself as the most exclusive among Democrats, adopting new limits on the number of members it will accept.

According to Rep. Mike Ross (D-Ark.), the group of fiscally conservative Democrats approved changes to its bylaws in early February that restrict membership rolls to 20 percent of the size of the full Democratic Caucus for the 110th Congress.

“As a member driven organization, the Blue Dog Coalition’s strength has always been derived from the ability of its members to reach consensus on issues put before them,” Ross, a co-chairman of the group, said in statement Wednesday. “In order to ensure that the Blue Dogs remain a cohesive and effective group, they have overwhelmingly approved new changes to their bylaws to limit their membership …

“This floating cap will fluctuate with each new Congress and ensure that the Blue Dog membership will remain an influential and moderate voice within the caucus for fiscal responsibility and strong national defense,” Ross added.

Several Democratic observers suggested that while the new bylaws could limit the coalition’s future growth, the Blue Dogs still could expand its influence over the Caucus, with a tightly aligned group more readily delivering votes.

Under the new formula, the Democratic faction would be limited to 47 members, leaving three vacancies in addition to the 44 lawmakers now on the membership rolls.

Whether the new limitations actually will alter the Blue Dogs’ composition, however, remains to be seen. In recent years, the organization has grown in large part from the addition of newly elected lawmakers.

The Blue Dogs have vetted classes of “Blue Pups” each election cycle since 1998, meeting with candidates to determine who will receive financial support as well as receiving pledges for membership. The group was established in the 104th Congress.

While most factions within the Caucus restrict eligibility for membership, primarily through ideological requirements or ethnicity, no other high-profile group has instituted similar numerical limitations.

Rep. Ellen Tauscher (Calif.), who chairs the centrist New Democrat Coalition, said that while lawmakers should adhere to the organization’s tenets, there are no specific restrictions on NDC membership.

“Our requirement is that Members be active,” Tauscher said, noting that NDC leaders did meet with candidates during the 2006 election cycle to recruit new members. “We’re not interested in press release New Dems.”

The New Democrats count 63 members in the 110th Congress.

Other organizations, such as the Congressional Asian Pacific American Caucus, vet would-be members on criteria ranging from ethnicity to interest in the organization.