Grover Norquist, president of Americans for Tax Reform, has been called the most powerful man in Washington. He is not the author of legislation, he is the author of a pledge.

Norquist's pledge to refuse to raise taxes was signed by 235 House members and 41 senators, and has dramatically affected practically every single bill in the 112th Congress, particularly the debt ceiling debate. There were precious few compromises by the GOP, because if they even sniffed a change in the tax code that would entail the wealthy paying more on April 15, it was a dealbreaker. A promise is a promise after all.

Then there's the National Organization for Marriage pledge that GOP Presidential candidates Former Gov. Mitt Romney, Former Sen. Rick Santorum and Rep. Michele Bachmann (R-Minn) signed, opposing gay marriage. There are plenty more concerning school choice, involvement in foreign military campaigns, etc., and not all of them are on the right.

"We've seen a proliferation of outside political groups who are making demands on politicians," said Stuart Rothenberg, editor and publisher of the Rothenberg Political Report, a non-partisan newsletter covering U.S. politics. He asserts that these groups are using the pledges to influence politicians even before they are elected. Then the groups boast of the signed pledges as indications of their strength and use them to raise money.

It's good for voters to hear politicians say concretely whether or not they believe in something, but the pledges are problematic in the long term because they limit the candidates from shifting their stances in the advent of new information.

"It's nice to have politicians take principled stands and stick with them, but we have to allow for changing circumstances," Rothenberg noted.

Of course, they don't always keep their word. In the 1980s and 1990s, there were a fair amount of term-limit pledges floating around, and for the most part, once elected to Congress, the politicians did not stick to them. They argued that after serving a term, they saw how important seniority was and that it would be counter-productive for them to leave. For the most part, voters were OK with it. So maybe the pledge dictatorship will not last forever.