I'm not taking sides, but it sure seems like Rasmussen robopolling produces better numbers for Republicans than other polls. Today, Rasmussen reports a narrowing, but still substantial 5-point preference for Republican over Democratinc congressional candidates.
By way of comparison look at Polling Report, which rounds up polling from all over. Different results. AP, NBC, Kos and Gallup in May showed preferences evenly split or in favor of Democrats. Only one poll -- Fox -- gave Republicans an edge and then it was only 2 points.