Interesting kudoz. To my surprise, there's no universal consensus on the translation.
I would probably choose:

Electoral exchanges between politicians and the mafia

but you have several options to choose from (the list below is not exhaustive).

Note that mafia is often capitalized but I refuse to do so, and not just for linguistic reasons.

Political interactions in contexts of presence and influence of criminal organizations
Therefore the political-electoral exchange was based on two main sources: the mafia groups supported the election campaign of the politicians by procuring votes for the different elections, and with the sums of money obtained from extortion, funded the election campaigns
https://ecpr.eu/Filestore/PaperProposal/60d56199-6d96-473f-8...

Electoral exchanges between politicians and the mafia
https://books.google.com/books?id=UAtoA5AKaf8C&pg=PA225&lpg=...

Political-mafia vote-rigging
http://www.coimgroup.com/doc_din/Organisation_management_con...

electoral political-criminal exchanges
http://www.tractebel-engie.com/wp-content/uploads/018/2015/0...

political and mafia-related vote-rigging
http://www.dlapipercentralcms.com/export/system/central-cms/...

Election vote-exchange between politics and mafia
http://www.sifinitalia.it/ENG/documenti/Modello 231_vers2015...

Electoral vote trading by politicians and mafia members
http://www.pininfarina.com/media/files/corporate_govenance/s...

Bargaining of votes between politicians and members of mafia
https://www.unodc.org/cld/en/legislation/ita/codice_penale/l...

political-mafia electoral exchange