As long as I've been paying attention to politics, I've noticed that no President ever does what he promised. I remember hearing the first President Bush say, "Read my lips: No new taxes." I was still in high school (I think) at the time, and I thought, "If I could vote for him, I would. He's not going to raise taxes. That's awesome!" What was one of the first things he did after being elected? Raise taxes.
If people voted on Presidents based on whether or not they kept their word, no one would ever serve a second term...and there are tons of Presidents who were in office for 8 years.
What it boils down to is this: people simply need to vote for the person they believe in, knowing full well that there will be disappointments.