President Bush isn't running for reelection, so public opinion doesn't matter.Not to pick on Random Brain Dribbles, but a recent post about the protests has a sort-of example. A better example is in a comment on this post at baldilocks.
The reason the abysmal public opinion of President Bush and his job performance is important is not so much the effect it has on President Bush himself. It's important because of its effect on leaders around him. There's less reason for congresspeople to make an effort to work with him because the President can't help them in their campaigns anymore.
It's also a signal to future Presidential candidates: don't do what he did. I thought that President Bush's first term was terrible, and I thought that voting for a second term indicated approval of the first. A slim majority of American voters saw things differently.
Poor public opinion of President Bush gives me some hope that the policies of the Bush administration are coming to an end. Congress won't cooperate with it as much, and future presidents won't be tempted to emulate it. This is not to say that what comes next won't be as bad or worse in a different way, but I'm keeping my fingers crossed.