President Obama has been criticized from left and right for failures and disappointments. He has failed to get much notable legislation passed since the first two years in his first term, he will (depending on your point of view) leave the world in a more dangerous and precarious state, and he hasn't restored our faith in governments. All of these "failures" stem from one thing. Obama hasn't dealt with a majority in the House since 2010 and lost his majority in the Senate. Barack Obama's biggest failure is allowing Republicans to flourish in the off-year elections.
As a progressive on most issues, I viewed Obama's election with a Democratic Congress as the beginning of an era that would be defined by how Democrats handle power. For reasons I haven't been able to fully figure out, Obama and his party have been repudiated loudly in the elections of 2010 and 2014. Republicans dominate more state houses and legislatures that I can ever remember. They hold the biggest advantage in the US House that they have enjoyed in my lifetime. They have assumed control of the Senate and have a decent chance of keeping control of that body after 2016, no matter who wins the presidency.
While Obama isn't the only reason why Republicans dominated the last two off-year elections, he has to be culpable to some degree. The very connection that allowed him to win two elections with clear majorities, something not done by a Democrat since FDR, seemed to be missing when he was on the stage campaigning for others. The very strategists that tailored his wins couldn't put forward a message that the country could get behind.
Now we are staring at 2016, with Democrats knowing that if their candidate doesn't win handily, there isn't much hope of turning the whole picture around until 2020 at the earliest. The balance in the Supreme Court is certainly at stake, and the picture of either a Republican trifecta or a Democratic executive branch cancelling out a far-right Congress is not pretty. Republican gains are particularly tough because when they have law-making power, they immediately take actions to help themselves in future elections. Ruthless gerrymanders and all manner of vote-supression laws are sure to follow.
This is the landscape that is here at this time. Win or lose in 2016, progressives and believers in good government need to redouble their efforts to elect more politicians of their own ilk and to limit or defeat Republican efforts.