As you watch the Italian election results come in this weekend, ponder the following seemingly contradictory statement: for some Italians in some regions of the country, the vote that is most likely to lead to the policies they most prefer being enacted by the new government would involve voting for their preferred party in the elections to the lower house of the Italian Parliament (the Chamber of Deputies) but for their preferred party's worst enemy - the party of Silvio Berlusconi - in the upper house (Senate) elections. How could this be?
The answer lies in what political scientists call "strategic voting". To understand strategic voting, it is first necessary to understand "sincere voting". A sincere voter ranks the parties or candidates, and then casts his vote for his top ranked party: the vote is a "sincere" reflection of the voter's top preference. A strategic voter, however, asks some sort of additional question before deciding whether or not to cast his vote for his top choice.
Usually this question is "will my vote be wasted"? The easiest way to waste a vote is to cast it for a candidate who has no chance of winning: think a vote cast for Ralph Nader, for example, in the 2000 US Presidential elections. Occasionally, a vote can also be wasted by casting it for a party that has already won an election, but needs a coalition partner to get above a minimum threshold in order to govern.
Strategic voting then might dictate voting not for your preferred party, but for its needed coalition partner; such behaviour is said to explain the unexpectedly strong performance of the Free Democrats in the recent German regional election in Lower Saxony.
But there is another type of strategic voting, trying to influence policy outcomes. Social scientists Howard Rosenthal and Alberto Alesina have demonstrated how it can be perfectly rational for Americans to vote for one party in a presidential election and another party in legislative elections if one's policy preferences are located between the two parties.
The current Italian elections, however, take this form of strategic voting to a whole new level, as they provide a set of incentives for voters to vote for and against the same party in one set of legislative elections to pick a single government. Here's how.
Italy employs a very unique electoral system (well explained here). In the elections for the Chamber of Deputies, whichever party (or pre-electoral coalition of parties) receives the most votes automatically gets a majority of the seats (54 percent to be precise) in the Chamber.
In the Senate, however, this "bonus" for winning is awarded not to the party that gets most votes for the Senate nationally, but rather there is a bonus awarded for whoever does best in each of 17 regions. So it is possible for parties to get the bonus in one region but not in another.
Furthermore, in Italy the government needs to have the "confidence" (that is, be approved by) of both houses of the parliament. So the winner of the Senate is just as important as the winner of the Chamber of Deputies.
To greatly simplify Italian politics at the moment, let's just focus on the three most relevant coalitions: former Prime Minister Silvio Berlusconi's right-wing coalition, current Prime Minister Mario Monti's centrist coalition and the main left-wing coalition under the leadership of Pier Luigi Bersani.
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(There is also an "anti-party" movement under the leadership of comedian Beppe Grillo that is doing very well in the polls, but as for now analysts think they plan to stay in the opposition regardless of the outcome of the election, we can leave them out of this discussion.)
The crucial fact about the balance of power between the three potential governing coalitions is the following: only the Bersani (left) and Berlusconi (right) coalitions have any chance of winning the bonus at either the national level or in any of the individual regions.
Therefore, if an Italian voter wants to see a government composed either entirely of the Bersani coalition or the Berlusconi coalition, he can vote sincerely in both the Chamber of Deputies and in the Senate elections.
However, there are many people who would like to see a Bersani-Monti coalition, and some of them even live in Italy. This will only happen if the Bersani coalition needs votes from the Monti coalition in the Senate, as the bonus for the Chamber of Deputies election winner ensures that whoever wins that election can rule on their own.
So with this scenario for the Senate in mind, consider first Monti's supporters. If the Bersani coalition is the plurality winner in the Senate vote in all of Italy's region, then Bersani can govern without Monti.
The only way then that Bersani can be prevented from winning all of the regions in the Senate election is if the Berlusconicoalition wins some of them. This means that (a) if you want to see Bersani ruling in coalition with Monti and (b) you live in a region where Berlusconi is actually competitive, the best chance you have of seeing Monti in the government is if you cast your vote for the Monti coalition in the Chamber of Deputies, but for the Berlusconi coalition in the Senate.
What makes this even stranger is that the exact same logic holds for more centrist supporters of Bersani. Without going into too much detail, Bersani's party has a more centrist (which today means more pro-economic reform, or more pro-austerity) wing, as well as a more traditional leftist wing.
Moreover, the other parties in Bersani's coalition are to the left of his party. If you are from the centrist wing of Bersani's party, you may actually prefer to have your party form the new government in coalition with the Monti parties than with the coalition partners with whom you are contesting the election.
Should this be the case - and should you live in a region of the country where Berlusconi is competitive - then even if your preferred party is Bersani's party, it still probably makes the most sense for you to vote for the Bersani coalition in the Chamber of Deputies election, but for Berlusconi in the Senate. Strategic voting indeed!
Will this actually happen? The Bersani coalition has spent the last decade battling against Berlusconi; the Monti government was put in power to clean up Berlusconi's mess. To say that some might find Berlusconi himself troubling - and the act of voting for him morally repugnant - is probably an understatement.
My Italian friends tell me that such voting behaviour is unimaginable. And yet, we've seen strategic voting occur in elections all over the world; we know voters are quite capable of figuring out how to use their vote to advance their own policy preferences.
As a political scientist, I am intrigued to see if this type of strategic voting actually does take place. As an observer of Italian politics, though, at this point I'm mainly just holding my breath.
Joshua A Tucker is a Professor of Politics at New York University, a National Security Fellow at the Truman National Security Project, and a co-author of the award winning politics and policy blog The Monkey Cage.
Follow him on Twitter: @j_a_tucker
The views expressed in this article are the author's own and do not necessarily reflect Al Jazeera's editorial policy.