Congress and the convention ???

One thing that puzzled me about the Democratic Convention just completed last night with a stirring call for renewal by President Obama.

During the three nights of inspiring speeches, there was not one single mention (that I heard)  of the need to take back the House and keep control of the Senate.    Yes, Obama needs four more years;   but he equally needs a Congress that won't be simply obstructionistic, as this one has been.

Yes, a number of the speakers were identified as candidates for Congressional seats, and there were passing references to the Republicans' intransigence;  but as an overall goal for the election -- the subject was simply not addressed.

Or perhaps it was obliquely addressed in Obama's saying to the audience, "only you can bring about the change.   You are the ones who make it happen."   And was the "you" to be understood as speaking through their Congressional representatives?  Was it simply to be implied that you not only have to go out there and vote, and get others to vote for president -- but also to elect a Democratic Congress?   Why not say it?  It's very true.

Was it a tactical decision to avoid putting the blame on Congress, as if it would make Obama look powerless?  Or did they want not to alienate Congress?   I don't get it.   Of course, the first priority is re-electing President Obama;  but close behind is giving him a Congress to work with.

Ralph