Q Day 6: Do Congress's Record Low Approval Rates Matter?

Another question:

[P]residential approval ratings have a lot of predictive power for election results. Seeing as Congress just hit an all-time low in approval (according to Gallup), I have to ask if Congressional approval has similar predictive powers?

Hey, that's an easy one -- John Sides posted about this back in June. Take it away, John:

Here’s the rub: when people dislike Congress, they punish members of the House majority and reward members of the minority.  Opinions about Congress are important even when controlling for other things that affect congressional elections, such as approval of the president or economic conditions in the country.  In the article, Jones finds that a ten-point decrease in approval would cost majority-party incumbents about 4 points at the polls.  It would also help minority-party incumbents by a smaller amount (just over 1 point).  Even more consequential for elections, these effects are larger in swing districts.  

That's from research by David Jones and Monika McDermott (book here; article by Jones here). Now, I'm only relying on John's summary (go ahead and read the whole thing), and there are as always important caveats: this time might be different for all sorts of reasons. But that's what we have, and it appears to be bad news for Republicans.