Iron triangle refers to the alliances among congressional committees, federal agencies, and lobbyists who share an interest in getting the same policy goals enacted. The term was popular in the political science literature of the 1970's and 80's, but is rarely used anymore. Senator McCain does not use it in the traditional political science sense, but has self-defined it as the connection among "money, lobbyists, and legislation."

"Iron triangle" implied that if a congressional committee supported a program, along with the federal agency that administered the program, and joined by special interest group lobbyists, a bond as strong as iron formed among the three, creating a juggernaut for passage of legislation that could not be stopped.

The term fell out of favor among political scientists because it was no longer an accurate description of changed political dynamics. A triangle no longer exemplifies the complicated structures generated by the fragmentation of complex issues. You rarely find just two competing sides to an issue anymore. For example, rather than one lobbying organization in support of agricultural subsidies, there are now more likely many individual groups, each fighting for a different product. Rather than just one federal agency implementing a new program, pieces of the program may now be owned by Agriculture Department officials, trade representatives at the Commerce Department, State Department diplomats, White House political advisors, and OMB budget analysts. In Congress, jurisdiction of complex issues is divided among multiple legislative committees and subcommittees, no longer falling just into the hands of one panel.

The nature of issue alliances has also changed: they are rarely permanent anymore. The bonds are less made of iron and more made of velcro. Policy-makers now tend to form issue networks as their interests coincide, and dissolve them when they conflict. Special interest groups who give financially to campaigns often give to both political parties to guarantee themselves access regardless of the electoral outcome. Members of congressional committees are often at ideological odds with others in their own party. Conflict is not limited to just across party lines, and cooperation ebbs and flows depending on the issue.

Another trend which outdates the concept of iron triangles is divided government. When the legislative branch and the executive branch are controlled by different political parties, conflicting political agendas make cozy relationships nearly impossible. Only when Congress and the White House are both controlled by the same party can strong alliances between the branches form.

Finally, recent decades have seen an increasing acceptance of spending restraints. Budget deficits have become political issues. It is very difficult to keep alliances together when resources are limited and competition for funds escalates. Whereas iron triangles were said to have so protected favored programs that penetrating them was impossible, today's fiscal reality is that numerous federal agencies have been downsized, programs have been eliminated or pared, and Congress has become as interested in saving money as in spending it.