I seem to remember an article by Kalecki about the political trade cycle (the very title?) and his little book Theory of Economic Dynamics. Although Kalecki did indeed predict political machinations, so far as I know that actual business cycles that have occurred have not transpired in any way that could be explained by Kalecki's putative causation. I think that in the end, Kalecki also agreed that capitalism only needed a correct economic policy, even if he was shrewder about the politics.
As to Keynesianism on economic development, I am pretty sure that it assumes that the normal operations of capitalism will develop all economies, presuming that comparative advantage is pursued. I think economic history refutes this. (And the absence of an analysis of imperialism in Keynesianism, which after all originated when the maps officially still read British Empire and French Empire should be quite an embarrassment.)
The world economy is not an exogenous factor. I don't think any Keynesian has even seriously thought about the long-term meaning of demand management in that context. And frankly, what monetary and fiscal tools could possibly mean in a world that doesn't really have a common currency?
Again, there is no reason that I know of to pretend to analyze the Greek situation apart from a general crisis in the world capitalist system. That's just foolishness. I don't think it's unique to political conservatives. That is obviously (I hope) why I didn't vote the poll.