The effect of leadership factored into this period, notably, 2 instances in which Mazzini could have led to the fall of the Roman Republic; when his spending policies created runaway inflation and when his preference for diplomacy actually led to its end by French conquest. Perhaps of greater importance was the leadership structures that existed, the revolutionaries were unable to replicate the levee en masse of the French revolution, whose success came irrespective of the unwillingness of vast swathes of its population to fight.
Examining popular support of course raises the question of popular support for what? Though this period (’48-’49 especially) is woven into the Risorgimento narrative, many of the territories seemed not to fight for Italy as a state, but their own territory as a state in itself. Both the Sicilian revolutions of 1820 and ’48 were separatist, as well as being crushed by whichever government happened to be in Naples. Despite being adjacent to each other, the government of Bologna neglected to aid Modena during the Austrian invasion of 1831. Piedmont-Sardinia, whose army was a personal one, during the spring of nations, whose leader declined assistance from other groups, exemplified how there could be an Italian state could be achieved by spreading the borders of one of the local states.
It would be inaccurate to ascribe the Risorgimento to be a popular one, that is one supported by the majority in Italy, because while it was true that most had a vision of Italy as a whole, theirs was not the same as any of the many other political groups in Italy at the time. The sharp increase in anticlericalism exhibited by nationalist groups after the Papal Allocution of 1848, suggests that the Italian population was divided by religion and political allegiance to the Catholic Church, whereas before there was a movement to create an Italian federation with the Papacy at its centre. A tangible result of the influence of Catholicism was the pressure on Napoleon III, by his Catholic political supporters, to end the Roman Republic during the spring of nations.
There were objectives common to nearly of all of the revolutionaries in this period, one of which was to resist foreign power, especially Austrian hegemony in the Italian states. The barrier to unification provided by stronger powers abroad was very great. Nearly every major uprising from 1830-49 was ended by foreign military intervention, especially Austrian. The weakness of even the strongest Italian state; Piedmont-Sardinia, relative to foreign powers was made apparent by its acceptance of the end of the 2nd war of Italian independence in 1859 as soon as its leadership discovered that France and Austria had decided on a peace.
So, the Risorgimento was a result of as well as hindered by the pressures exerted by power structures in Europe, the congress powers in particular, the same can be said of popular support if their tacit support by non-action can be counted as support for any result.