President Barack Obama has, unfortunately, not done a very good job of cleaning up the mess left by his predecessor. America is still deeply embroiled in two distant wars that look increasingly unlikely (if they ever did) to achieve anything of benefit. And unemployment remains high following the financial crisis which resulted from the previous government's letting big bankers run wild. Even the Gulf oil spill, though it occurred under Obama, can be blamed on the lax regulatory regime instituted during the Bush ers - but Obama's administration is perceived as not having handled it well.
So how are American voters going to punish the Democrats for their ineffective handling of these problems? If polls can be believed, probably by handing control of Congress back to the very party that created all the problems in the first place, and has come up with no better plan for resolving them. Pretty smart, huh? I am reminded of Winston Churchill's maxim that "Democracy is the worst political system, except for all the others".
On the other hand, perhaps they may have been deterred from considering a possible third party vote by looking at Britain, where millions of people voted for the Liberal Democrats because they were sick of "New" Labour and didn't want the Tories back in, only to see their leaders jump into bed with the Tories in their greed for a share of power. In the end, another political maxim says it all: "Whichever party you vote for, the government always gets in".