When a US Senator or Congressional Representative signs a no tax pledge, is this in conflict with the Oath of Office each of them took when elected?

The Oath of Office for Senate is as follows:

I do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I take this obligation freely, without any mental reservation or purpose of evasion; and that I will well and faithfully discharge the duties of the office on which I am about to enter: So help me God.

The Text of the Tax Pledge is as follows:

I pledge to the taxpayers of the (this) district of the state of…............, and to the American people that I will:
ONE, oppose any and all efforts to increase the marginal income tax rates for individuals and/or businesses; and
TWO, oppose any net reduction or elimination of deductions and credits, unless matched dollar for dollar by further reducing tax rates.

Do you see a possible conflict here, or have I just heard too much progressive propaganda?