You're showing the low number of congress in general - both parties. This brand new poll shows the dems with a hefty lead. Even if this poll is an outlier... I have to wonder... Why the heck aren't the repubs leading every poll by 20 points? What else can the dems do? Why can't the repubs capitalize? Obama is at 48% gallup approval rating today. Nothing sticks to the guy, and he's just ramping up for the fall.
IMO, the tea party shot their load about 6 months too soon. 
Even if you only look at Gallup and not others that contradict Gallup, a six point lead is hardly "hefty." Usually, the margin of error is four or five percent.
You'll never see any party up by twenty points, consistently. There is a core group from each party that will always vote along party lines.
The fact Democrats are projected to lose both the House and Senate by
Democrats should tell you all you need to know about how much trouble they are in.