Corruption makes the world go round. That, in a few words, is the basic idea of Bernard Mandeville’s The Fable of the Bees, a work that became a basis for liberal thought, most famously in the case of Adam Smith. This long poem tells how a corrupt beehive — in which “no calling was without deceit… every part was full of vice” — through the moral intervention of a higher power, ceases to have vices, and it also ceases to work!
Now something similar could be said of politics. Of course, it may not be that corruption is a necessary feature of all politics at all times, but it is certainly a feature of modern state politics, both in the Global North and Global South. That is why it is an especially slippery area for “progressive” parties or individuals that enter into the state and from there attempt to improve the situation of the masses by making popular reforms.
The most basic feature of state politics today — that is, electoral and institutional politics in a modern democracy — is that it requires enormous amounts of money. On the one hand, election campaigns everywhere involve a great deal of money, and, on the other hand, there are systems that structurally “depend on” corruption. For example the Brazilian state systematically pits the legislature against the executive branch, which needs to buy its members off to govern. 
Where then is the money for parties such as the PT in Brazil or the PSUV in Venezuela to come from? From dues paid by the impoverished masses? There was a time when important workers’ movements, such as Chartism in England, could be financed by the dues of their humble militants. But that was before the top one percent came to control 99 percent of the world’s wealth. Also, today the progressive small bourgeoisie, that might be relied on to fund movements for change, has almost completely ceased to exist.
The logical upshot of this unfortunate, unfair situation is that in our time the money for left parties’ campaigns and other operations must be acquired (usually diverted) from the state itself. It should be noted that much, though certainly not all, of what is identified as corruption in Latin America’s left goverments today is money that has been diverted for political, not strictly personal, purposes. 
This is exactly what Brazil’s Dilma Rousseff is accused of doing: shifting money from one account to another to pay for social programs that were presumably important for her reelection in 2014. It is also what a number of Chavist politicians are doing in amassing money in the present moment. That money is generally for campaigns and for political positioning in preparation for upcoming scenarios.
Corruption of this political kind is indeed a problem for the left. Its abolition should be aggressively pursued. Yet if eliminating corruption does not change the whole form of politics for all players in the country and instead amounts to just ceasing to be a player, it is a futile project for the left.
It should be remembered that Joseph Stalin, with Lenin’s approval, robbed banks to finance the Bolshevik party. Chavist politicians have also robbed banks: their own. This may seem relatively lacking in glory, but at least most of the time it is also in the service of political ends.
It is possible that, today, a specific form of politics — one that is triangulated among parties with large amounts of money, elections that involve mass-media budgets, and expensive top-heavy states — has reached the limits of its effectiveness for the left. In fact, the current corruption scandals in Latin America, such as those that have emerged in Brazil in the past few years, are best understood as a symptom of the weakening of left governments, due to their inability to produce results, than a consequence of increased real corruption or of new evidence in the hands of their enemies.
Exposing this kind of corruption is a questionable project. If it comes from the political left, it risks being like the moralizing power in Mandeville’s fable, which does more harm than good. Another option is simply destroying the beehive. Effectively, the beehive is the top-heavy state that rests on and reflects a top-heavy — that is, capitalist — civil society.
Transforming both that state and society is an old Marxist idea, and perhaps its time has come.
 Perry Anderson, “La crisis de Brasil,” http://lhblog.nuevaradio.org/b2-img/anderson_brasil.pdf.
 Of course, strictly personal corruption exists. Yet much of it is an almost inevitable consequence of individuals managing “gray” or illicit political money. Sometimes, too, personal enrichment results as the “second-best” option in a failed political project.