I call bullshit on that poll. People are not morons. If disapproval rating at congress was so high according to a representative poll group, then why aren't people voting in people that they do approve of? House terms are short. Senate terms are long but I don't think this 86% number would have happened overnight.
These days you're virtually guaranteed a disapproval of nearly 50% on the day you step into office.
(warning: oversimplification ahead, but I think it's a reasonable model to start with)
With the subtlety of the political chess match, the parties first choose polarized candidates in primaries. That's because it's generally the party hardcore who vote in primaries, not the moderates. Then in the general election, they play capture the centrist vote. When they're both at top form, the election margins are going to be razor thin.
Because the candidates were chosen in such a polarizing manner, they will largely be toxic to those on the other side of our imaginary single left-right dimension of political discourse.
(of course, this breaks down in gerrymandered districts where the political machine has ensured a safe seat)
EDIT: Now, factor in the typical model for marketing most high-profile candidates (at least this is how it seems to me). It seems that most people don't have the opportunity to vote for candidates they like anymore. Instead they're frightened by the bogeyman on the other side. "If you don't vote for the guy from our party, look at who's going to get the post instead -- and that will tilt the majority in Congress toward that other party of anti-Americans". The result, I submit, is that most people despise the guy from the other major party, but they don't like the one they did vote for, either. So it's not hard to push that disapproval rating even farther.
Remember that a good bit of disapproval is of "the other guy". It's very easy to disapprove of congress as a whole, but continue to vote in your own incumbent because the bacon they bring back is for /you/. The bacon everyone else brings back is "wasteful".
