Ian Millhiser, writing for Think Progress, says that if the Democrats don't win the White House in 2016 then Democratic power, and progressive ideals, might be impossible for a good long time.
Much of the current GOP power is based on gerrymandered states. Democrat candidates for the House received 1.4 million more votes than GOP candidates, yet the House is solidly in GOP hands. Dems would need to win House seats by over 7% to take it back. Put another way, GOP power isn't going to end until gerrymandering ends and absent a string of state constitutional amendments gerrymandering ends only when the Supremes say so.
Yet, in a 2004 case the Supremes said they would dismiss cases involving political gerrymandering. Add to that the Court's approval of voter ID laws and the gutting of a key provision of the Voting Rights Act. So the only way to curb GOP power is to change the Supremes.
When the next president takes office conservatives Scalia and Kennedy will be 80, and progressives Ginsburg and Breyer will be 83 and 78. That next president has the potential of increasing the progressives by 2 – or increasing the conservatives by 2. And they would be solid conservatives, acceptable to the Fundies and the Tea Party.
Under a Democratic president's Supreme appointees overturning gerrymandering, banning voter IDs, and reinstating the Voting Rights Act should be straightforward. A GOP president's appointees would entrench those decisions, then be willing to gut any initiative by a future Democratic president or Congress. Keep in mind there were justices willing to gut the Affordable Care Act, rather than defer to Congress.
Getting a Democrat into the White House in 2016 is critical to the progressive cause.