In French politics, a cohabitation is the informal name used to refer to a situation in which the President of the Republic and the Prime Minister are from opposed political parties.
Parliamentary vs. Presidential regimes
In modern democratic countries, most regimes either follow a presidential or parliamentary form.
In a presidential regime, the principal character of the government is the Head of State (most often called the President) who is granted great political power by the Constitution and the legitimacy to use it from his popular election by universal suffrage. This President's power is balanced by a theoretically equally powerful elected representative body. As you probably figured, I just described the regime of the United States of America. It is the earliest and arguably the only truly presidential regime in the world, and every other constitution which seeks to create one is inspired from this wonderful document that is the Constitution of the United States of America.
In a parliamentary regime, the titular Head of State is a more or less powerless figure whose role is largely symbolic. This Head of State can be either a crowned head or a President who is elected by a political body and therefore has little popular legitimacy. The real political power, you guessed it, rests with the Parliament—for the purposes of this writeup, I will call the representative body Parliament, even though it may be called differently in different countries. The government emanates from and is dismissed by the representatives, and the executive power is not wielded by the Head of State, the President, but by the Head of the Government, the Prime Minister. The first parliamentary regime evolved out of the history of England and the United Kingdom. It was mimicked by all countries which had a regal legacy and wished to keep their crowned head even as they switched to democracy. It was also applied by many others simply because it's much easier to implement a parliamentary regime than a presidential one, which requires both separation and collaboration from the executive and legislative branches of the State.
Cohabitation in France
How France differs from the rest of the world (in this instance...) is that its Constitution incorporates elements from both models. The French regime is parliamentary: the elected representative body nominates and dismisses the government and its Prime Minister. However, the President is not at all powerless. Like in a presidential regime, he is elected directly by the people and is granted all the powers of the Head of State of a presidential regime, and even more, notably the power to dissolve the National Assembly, the lower house of the French Parliament.
The spirit of the Constitution keeps the idea of a parliamentary regime where the Head of State is a figurehead who represents the entire Nation, which is the President's main job. However, this figurehead is not at all the proverbial powerless figurehead. In the minds of the French, or at least those who wrote the Constitution, the Head of State cannot truly represent the Nation if he does not lead its Republic, and he is thus given the power and legitimacy to do so.
The President of the French Republic is therefore a dual character: he is the representative of the entire Nation, who is supposed to stand above party interests and rivalries in order to make real decisions; but at the same time he is a politician, a party leader, and therefore also represents the specific interests which got him his job. This is where the Prime Minister comes in: he is appointed by the parties who reign in Parliament to carry out policies which have been decided by the President. That way, he can keep his personage and prestige above the hubbub of politics. It's also a very useful political device: the President can decide on unpopular reforms and since it will be the Prime Minister who will carry them out he will take the heat (and often, ultimately, the fall) for them.
In theory this is perfect and in practice has worked smoothly—if the President and the Parliament majority are the same party. In the United States, where there is a strict separation between the branches of government, the election of a Congress opposed to the President doesn't affect his branch directly. But since in France the Parliament can dismiss, and therefore effectively nominates the Prime Minister, the duality of the executive branch that was the Constitution's strength becomes its weakness: who's in charge?
At this point it's important to mention how important custom is in constitutional law—more so than in any other branch of of law. Most Heads of State in parliamentary regimes have theoretical powers similar to those of a powerful President, but those powers are never applied—think what would happen if the Queen of England, who technically nominates everyone who holds public office, tried to actually decide who to nominate, let alone tried to make policy. But even besides regal regimes, there are other similar examples. The Constitution of Portugal grants large powers to the President, but since 1976 the real party leaders have only ran for Prime Minister and made sure only people with no support would be appointed President, which makes the Prime Minister the country's effective leader and policymaker. Conversely, American Constitution scholars can tell you about the 1860 impeachment attempt on Andrew Jackson. Had it succeeded, this system of enforcing penal responsibility could've evolved into one of political responsibility and America's presidential regime would've become parliamentary, without changing a word of the text of the Constitution.
The French Constitution grants enormous powers both to the President and the Prime Minister. If you read the text of the Constitution, without prior knowledge of French history or politics, it would be impossible to say which is the real leader of the Republic. It is really only because Charles de Gaulle, the first President to use this Constitution, established it, that there is a custom that the President is the leader and the Prime Minister is his subordinate. Since de Gaulle was, if not the author, the instigator of the Constitution, he basically established through his presidency how it would be used and in what spirit. In keeping with this spirit, there would never be a cohabitation: since a President who loses the parliamentary elections would be considered to no longer have the people's approval, he would resign. However, there is no obligation of this in the letter of the Constitution, so cohabitations can and do happen.
The first began after the 1986 elections, which were lost by François Mitterand's party and brought Jacques Chirac to Prime Ministership until 1988. There was an other period of cohabitation during Mitterand's presidency between 1993 and 1995, and the third one and longest so far happened when Lionel Jospin became Jacques Chirac's Prime Minister from 1997 to 2002.
Everyone hates the cohabitation, and with seemingly good reason: to a politician who's in a cohabitation, his best interest is to try and stall the other guy. With the President's main concern being stalling the Prime Minister and the Prime Minister's job being to ruin the President's shit, nothing gets done, and the country only runs itself instead of being run by policy as it should be.
Well, at least, that's how the worst case scenario plays out. Most of the time the Prime Minister just becomes the effective leader of the regime, because he is the Head of the government and has control of the Parliament, which makes the laws. Perhaps more importantly, the Prime Minister runs things because his party won the elections, and therefore the President's party lost, therefore it is understood that, in the interest of democracy, the President should step back to the role of the Head of State of a parliamentary regime. This is also a smart political move, since the President can basically let the Prime Minister be blamed for everything bad that happens (as is always the case) and prepare for the next elections.
Everyone who was anyone called Jacques Chirac an ignorant, bumbling fool when he dissolved the Parliament in which he had a sweeping majority, in a context where the opposite party would win, and did. We had the longest period of cohabitation in history, an entire parliamentary term, but Lionel Jospin, who had been Prime inister for that time, got positively hammered during the 2002 elections, as with every other politician who has underestimated Chirac.
The cohabitation is widely believed to be the plague of the French Constitution, and the remedy which was thought up during the seventies but only recently applied was to shorten the President's seven year term to five years. That way, the elections for the presidency and the Parliament would happen at the same time so a conflicting choice wouldn't be made.
This reform is five to ten shades of wrong. First of all, a seven year term is already short for long term policies. The presidents who left their mark were those who served for more than one term; some argue that most presidents will be reelected and that effectively they're not shortening the term from seven to five but extending it to ten years. That is highly unlikely. It's also unlikely that what routinely happens in the United States won't happen in France: during simultaneous elections, opposed parliaments and presidents can be elected at the same time.
So what happens is that the President's position is weakened. Not just because his term is shortened but because he gets elected along with the Parliament. The outcome of the Parliamentary elections, ultimately, is going to be what drives policy: if the President doesn't get to make policy, it's because he lost the Parliamentary elections; and if he does, it's because he won them. Therefore, if the Parliamentary elections drive policy, then the guy who wins most from them is going to be the real policymaker. The five year term puts a real risk of our regime becoming a parliamentary regime, which, as our Third and Fourth republics have shown, is not meant for France. What makes our Constitution grand is that it puts the President above the fray of the parties, not by removing his power like in other regimes but by giving it to him.
But, what's so bad about cohabitation, really? It's sometimes a rough ride, but this wouldn't be planet Earth if there wasn't a rough ride every once in a while, especially in politics. Lionel Jospin's cohabitation went smoothly except when he tried to meddle with foreign policy, which Chirac felt was his "reserved domain." But otherwise, his government and Parliament majority set policy, with the President retreating peacefully to his role as a parliamentary Head of State.
The dean of a famous French law school, Georges Vedel, said that the best thing about the French constitution is that it is so "rich with opposed virtualities." It can be intepreted many ways, and can be made to fit the times and persons who use it. The idea that cohabitation is bad has been so ingrained into our brains that we no longer wonder "Why?" Because it's not explicitly mentioned in the Consitution? So what? Because it's not what de Gaulle had in mind when he built the Constitution? Once again, I'm as gaullist as the next guy, but so what? The great man's word isn't gospel. And second of all, how stupid do you think he was? It's pretty obvious from reading the text of the Constitution how it can be diverted.
Ideally and in de Gaulle's intent, the President should resign after his party lost an election, because it means he was disavowed by the people. But there's a reason why he didn't put it in the letter of the Constitution. The Constitution is rich with opposed virtualities, and this is why the cohabitation is not a big deal. The cohabitation has become as smooth a ride as it can be, and it is in keeping not only with the letter but the spirit of the Constitution. However, the five year term will be a big deal, but by the time anyone realizes it, it'll be too late.
vuo sez the Finnish system is also semiparliamentary. there are two things that differ in here. first of all, the president can't be a member of any political party. he is only The President of the Republic: he can't be "President, and..." presidents retire or move to international politics after their term, so they don't need to "worry about tomorrow". moreover, the idea of consensus politics is firmly rooted in the culture. thus, a strong president like Kekkonen is virtually unstoppable - his opponent has to be of the same caliper and that's not as easy as you'd think. thus, cohabitation tends to be pretty peaceful compared to that what you describe in France.
for example, now Halonen (soc.dem.) and Vanhanen (center) are "cohabitating". haven't seem much political Battleship games between them, just disagreements any two people could have, same party or no.
- Hugues Portelli, Droit constitutionnel
- Georges Vedel, Droit constitutionnel
- Elisabeth Zoller, Alternance et cohabitation