Francesco Oggiano, the author of "Beppo Grillo Parlante", told CNBC on Monday that Renzi would resign "one minute after the result" if the referendum produced a win for the "no" campaign .
Effectively, Oggiano explained, these reforms would result in a reduced role for the upper house Senate and limit the influence of regional government.
Italy's Five Star Movement (5SM) party is strongly against constitutional reform and, if opinion polls are to be believed, 5SM is firmly on track to be on the winning side in December.
In fact, 5SM hopes to capitalize on any momentum gained in the event of a referendum victory and possibly pip Renzi's Democratic Party at the next election, which could be triggered as early as spring 2017.
Populist parties throughout Europe celebrated the victory of Trump last week with far-right groups in France, the Netherlands and Germany buoyed by his surprise win.
Oggiano believes Italy's 5SM's support of the "no" campaign ultimately boils down to its opposition on a new electoral system that it believes is combined to the constitutional reform.
He said, "according to the Five Star Movement, people won't be able to choose their own representatives in the parliament and this is the most important point."
"The result (of a 'yes' victory) would be a parliament full of bureaucrats chosen from their parties that, once elected, will just get to satisfy their leader instead of people's needs," he added.
Renzi argued in an open letter to Italian citizens on Friday that a "yes" vote would make Italy stronger.