The math in the Senate is horrible for Democrats after two wave elections. Democrats defend 19 seats to the Republicans’ 18 this year, and I’d say there’s a 50/50 chance of Republicans taking back the Senate this cycle. The Senate looks worse for the Democrats from there. In 2012, Dems defend 23 seats to the Republicans’ 10. If Obama’s approval doesn’t get any better, its possible Republicans could have a filibuster proof super-majority just two cycles after the Democrats won a similar number of Senate seats. In 2014, Republicans defend 13 seats and Democrats defend 20. It seems likely therefore that after the next two cycles there will be a Republican super-majority in the Senate, perhaps even a Conservative one. After three cycles, the chances of Conservative Senate dominance are even higher. Keep in mind also that the Senate is a Republican chamber because of the extra weight given to states with low populations, which are more often Conservative states. This helps Republicans to pick up Senate seats, and also to hold them for the long term. This is especially true in the Senate due to its strong traditions of seniority which mean that many of these Republicans will serve in the Senate for decades as their power and utility to their home state voters grows.