Norquist's Pledge extracted from members of Congress commits "a member to oppose and vote against any effort to raise the federal income tax on individuals or corporations."(Americans For Tax Reform) In addition to prohibiting direct increases, it also prohibits ending loopholes or deductions, since they likewise raise taxes.
The oath which each member of Congress takes requires the support and defense of the Constitution "without any mental reservation" and a promise to "well and faithfully discharge the duties of the office." Vowing never to raise taxes directly or indirectly is certainly a "mental reservation,". Taxes are certainly not mandated by the Constitution, but they are clearly authorized and allowed by it. Thus an elected member of Congress in carrying out the oath of office would be expected to make legislative decisions based upon the facts and circumstances presented at the time. To commit in advance to a position of no taxes in the Norquist oath, without the necessary knowledge seems to be a dereliction of the duty imposed upon lawmakers, particularly when the commitment is made at the instigation of a private organization.
The current pledge was not the subject of public objection originally, probably because everyone prefers not to have their taxes raised. But suppose the pledge was not to raise taxes on corporations only, or taxes on gas, or taxes on tobacco? If the promise was to aid a specific interest group, there would be no doubt as to its impropriety. But should it be the content of the pledge that makes the difference? Should the mere fact that it favors or is favored by most people render it acceptable?
But in fact, we have come to find out that the current Bush tax cuts have favored the top 2% of the population, to the detriment of the 98%. Along with the fact that those tax cuts have created a tremendous economic deficit which has brought much hardship on the economically disadvantaged. Even so... the Congressional members who are most bound by the Norquist pledge, ie. Republicans, refuse to agree to tax hikes that are desperately needed in order for the government to fulfill the needs of those citizens who are in need.