From Meg Greene, here is the clearest explainer I have seen, here is one short excerpt:
There are clear reasons to vote for and against the constitutional reform. If only most Italians were actually voting with these in mind! According to one recent survey, only one in ten Italians were going to cast their ballot in response to the actual constitutional reform proposed. Because Prime Minister Renzi said he would step down in the event of a “No” vote, many Italians are casting their vote in favor of or against the establishment. Voting against the establishment means a lot of things, but given that the main opposition party, the Five Star Movement (M5S), has polled neck-and-neck with the governing Democratic Party (PD) this year it amounts to tacit support for this populist, anti-elite, anti-European party.
There is much more at the link, here is one significant point:
If the “Yes” vote wins on Sunday, Mr. Renzi will be strengthened in the short term but, given the Italicum, could be weakened in the next election. The result may be a government led by the M5S that may pursue a referendum on Italy’s membership of the Euro.
We will soon know more…