Visualize this scenario: A group of businessmen visit a Congressional candidate and ask him to sign a written pledge that he will not raise their taxes, reduce or eliminate their subsidies, deductions or loopholes. In exchange they promise that they and like-minded persons will vote for him and provide financial support for his campaign.
The reality is that in exchange for surrendering a right and power that he possesses as a Congressman to do any of the foregoing, he promises to forgo that right and power in exchange for their votes and support, and they, in turn, are assured substantial financial benefits. One might argue that candidates can certainly put forth platforms with the same commitments, but I respectfully suggest there is a great difference between a written pledge instigated by a specific private group and a statement of general principles and even firm promises in a campaign platform.
There is no quid pro quo in a platform. There is a hope that votes will result from the positions taken, but no direct promises or commitments are involved. There is a proliferation of political pledges involving marriage, "cut, cap and balance", abortion and others, some in ridiculous detail. The pledges are more likely enforceable in the voting booth rather than in a court of law.
I suspect that the courts would find the contracts unenforceable either as against public policy or simply illegal. I can envision a disgruntled supporter suing to obtain the return of his campaign contribution based upon a violation of the pledge, but I think the implicit threat is more one of political power rather than legal enforcement.
Can you imagine a person being selected for jury duty who has signed a written pledge never to find anyone guilty -- or anyone not guilty, or not to rule for a plaintiff in a malpractice case because it will increase premiums, or against a drug company because it will increase health care costs, etc. We expect juries to make decision based upon the facts presented free of pre-judgment and personal bias. Should we not expect the same of our elected representatives?
The analogy may not be totally apt, because politicians are elected because of their positions and impartiality is not a prerequisite. They are partisans, but to cling to commitments made to private groups irrespective of whether or not to do so is in the best interests of the nation would seem to be a violation of their duty, and promising to do so may well be a crime.
In my opinion, it is certainly a violation of their congressional oath of office which they take "without any mental reservation". Commitment to dearly held political beliefs is to be commended; but swearing blind allegiance to them is not.