BLOCS, a name given to organized voting groups in American legislative bodies, and more loosely, to associations of pressure groups attempting to lobby in American legislatures. In either case, the purpose of organizing a bloc is to create a group of legislators who will vote together consistently on certain issues. Blocs are highly organized, are based on closely shared interests, and command a high degree of loyalty from their members. A farm bloc, a protectionist bloc, a wet bloc, a dry bloc, a progressive bloc, and a veterans' bloc were all active in Congress during the early to middle twentieth century. After World War II the veterans' bloc and the protectionist bloc lost considerable influence. A labor bloc and a civil rights bloc rose to prominence in their place, but neither had an organization in Congress.
The rise of political action committees (PACs) in the late twentieth century supplanted blocs, making PACs the major lobbyists in Congress. The intensification of congressional partisanship during the 1990s weakened the power of bipartisan blocs, but it simultaneously strengthened the hand of ideological blocs within the two major parties. By 2002 virtually every bloc drew on PACs for fund-raising and congressional lobbying.
Sheppard, Burton D. Rethinking Congressional Reform: The Re-form Roots of the Special Interest Congress. Cambridge, Mass.: Schenkman Books, 1985.