The most common hallmark of the left’s magical thinking is a failure to recognize that Congress is a separate, coequal branch of government consisting of members whose goals may differ from the president’s. Congressional Republicans pursued a strategy of denying Obama support for any major element of his agenda, on the correct assumption that this would make it less popular and help the party win the 2010 elections. Only for roughly four months during Obama’s term did Democrats have the 60 Senate votes they needed to overcome a filibuster. Moreover, Republican opposition has proved immune even to persistent and successful attempts by Obama to mobilize public opinion. Americans overwhelmingly favor deficit reduction that includes both spending and taxes and favor higher taxes on the rich in particular. Obama even made a series of crusading speeches on this theme. The result? Nada.
Does the writer must really think that 'the left"(really left undefined and is actually made up of many constituencies) does not understand the different parts of government? I would say that given what I've seen come out of the mouths of their Republican peers, it would be those on the right who do not understand this concept. Anyway. "The Left" certainly did understand that congress is a co-equal part of government and that is why "the left" voted in a majority of Democrats into office. That 6 months represented a golden opportunity to do a lot of things and after the disaster that were the Bush years they should have gone for it. But that assumes that the Democrats are actually an "opposition party" as opposed to the upper lip of the same beast.
Secondly, in regards to the filibuster, the Democrats ought to have called the Republicans to task for that. To me these threats from the Republicans are like the the bank robber who comes in and puts his finger in his jacket to make it look like he has a gun and demands that you hand over the cash. One response is to do whatever the robber wants, in which case the robber gets away with robbing a bank with the threat of a weapon but never having to actually show and prove. The second thing is to aggravate the robber to get him to show that he actually has the weapon. Of course that tactic takes risk and someone might get killed. BUT the upside is that you know once and for all whether this robber actually has a weapon and he certainly will not attempt the "finger in the pocket" move again. But this is the problem with Democrats (again assuming they aren't the backside of the coin): They simply are not willing to risk pain. Once the enemy (or the opposition) finds your weak point, do expect them to hit it every time you enter the ring.
I'm not even going to get into the taking the public option off the table at the very beginning of the health care debate. That was simply inexcusable.