Effectively, the Italian election campaign is already in full swing, so I tried to start collecting some data to see what we are about to face. If I have time and manage to get some good data, I'll try to replicate the analysis I made for the US election (surely Italy needs its own version of Nate Silver too?).
However, there are quite a few differences in this case. First, the availability of data is not necessarily so good. I could find some downloadable lists of recent polls. But for almost all, the only information provided was about the estimated proportion of votes (with no summary of sample size or uncertainty). [Of course, I'm not saying that such data don't exist in Italy $-$ just that it was far easier to find for the US].
Second, Italy is very much a multi-party system; so I guess it is a bit more complicated to produce predictions and modelling, because you can't just use simple-ish Binomial assumptions (e.g. you either go Republican or Democratic). This makes for more complex interactions as well, since probably there is a level of correlation in the voting intentions towards parties that may (but also may not) eventually ally in coalition to form a government.
Anyway, I quickly played around with some data I found on recent polls (in fact this goes back to 2007). The graph below shows the voting intention (as percentages) for the two main parties (PDL in blue is Berlusconi's party, while PD in red is the "centre-left" Democratic Party). Also, I plotted the relatively new "Movimento 5 Stelle" (M5S, or "5 Stars Movement" $-$ I've already complained about the names of Italian political parties; I really don't know where they get them!).
The vertical lines indicate:
- The time when news that Berlusconi had attended the birthday party of 18 year old Noemi Letizia got out. This effectively started the scandal... what's the word I'm looking for? "linking"? Berlusconi to young girls;
- The time when Berlusconi was sent to trial for a reference about a sexual relationship with the teenager El Mahroug, aka "Ruby Rubacuori";
- The time when Mario Monti took over as PM, following resignation by Berlusconi amid concerns about the possibility of Italy defaulting its debt.
It seems to me that three things stand out from the graph:
- PD are sort of stable, around 30%. The current increase in the voting intentions may be due to high exposure in the media related to the primary elections that they held to determine the candidate to lead the party into the next general election;
- PDL are plummeting in the polls, and at least the first of the three time points I mentioned above seems to clearly mark the beginning of this decrease;
- M5S seems to have captured much of the votes lost by PDL (of course this is absolutely partial, as there are other 2 million small parties in the fray; nonetheless it looks like a clear trend).
Of course, there is so much more to this $-$ simply because no party is likely to win enough votes to govern on its own. Thus other players, like La Lega, usually Berlusconi's allies; or relatively recently formed SEL (Sinistra, Ecologia e Libertà $-$ Left, Ecology and Freedom) who are likely to support the Democrats, will certainly play a very important role.
I'm tempted to say that if PD keep their focus and choose reasonable partners in coalition, they should be able to hold on their core voters and gain enough to (comfortably?) win the elections. But (beside the fact that the campaign is just started and it's not even clear whether Monti will make himself available $-$ and if so, who with), this being Italy, crazy stuff can always happen...