the midterms referred to are local council elections that do not have any impact of Parliament directly, but they speak to the state of the parties nationally and will affect party morale

Omnishambles. It is a great word to encapsulate the government's serial misjudgments and misadventures, from granny taxes and petrol panics to the boomeranging budget and Theresa May's lost day. So I am not surprised that Ed Miliband chucked it at David Cameron in the hope that it will lodge in the public mind as the definitive, damning description of the coalition. The word does not, though, help us all that much with the large, long-term question raised by the most torrid period for the coalition since its inception. Does this mark a significant turning point or is it merely a passing blip?
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It is usually rash to read too much into midterm elections, but the outcome of these contests will nevertheless matter hugely to the national picture because of their impact on the morale and standing of the parties. As one of the prime minister's senior aides puts it: "They will set the weather from now until the party conference season." Convincing gains for Labour will give the opposition confidence-building momentum and open more space for Ed Miliband to act boldly. A better than expected performance by the coalition parties will conversely make it easier for them to draw a line under this miserable period for the government and turn the pressure back on the Labour leader. Which means that, even before a single vote has been counted, both sides are trying to shape how these elections are judged by the media and viewed by the public. For they know that it is not just the result that matters, it is how the result is interpreted.
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Whether the omnishambles represents a lasting turning point in political fortunes will at least in part be determined by how the parties react to it. If these elections are seen as a disappointment for Labour, then the coalition will breathe a bit easier because Ed Miliband will face renewed doubts about whether he is a convincing candidate for prime minister. If these elections are seen as confirming that the coalition is in deep trouble, then the heat on them will intensify and with it the risk that the government will go into a self-consuming downward spiral. The night of 3 May will be a long one for all the party leaders. What you might call an omnisweat.