They assume that the people who voted for them before will grumble a bit, but vote for them anyway.
Examples are Nixon saddling the U.S. Taxpayer with the hideous Food Stamp Program, and 41's infamous "Read my lips. NO NEW TAXES!"
It never occurs to politicians that their base of support perceives a compromise as a betrayal of trust. No, they just assume that we will still vote for them, regardless of their betrayal.
Far from surprised, my friend: President Bush is right on track to being another one-term President who was voted OUT of office, just like his Dad was.
What is sad, is that the democrats have NO ethics, so when they are voted in, by default, they drag the rest of our Republic down into their corrupt filth.