In some semi-presidential countries cohabitation is very rare. When there are synchronised or near-synchronised presidential and legislative elections and when there is one dominant party, then cohabitation is unlikely to happen. Also, when there is a highly fragmented party system, cohabitation may be somewhat less likely to occur as the chances of the president’s party not being represented at all in government is pretty slim.

In some countries, though, cohabitation is likely to be more prevalent. In particular, cohabitation is more likely when there are ‘mid-term’ elections and where there is a two-party system or a clear two-block system.

While many countries have experienced cohabitation and while a number, such as Bulgaria, France, Lithuania, Poland, Portugal, have experienced it more than once, a couple of countries stand out as being particularly cohabitation-prone: Sao Tome and Mongolia.

In Sao Tome semi-presidentialism began with the 1990 constitution. Since this time, there have been six cohabitation prime ministers.

The first presidential election in 1991 was a reaction against the rule of the former single-party regime of the Movement for the Liberation of São Tomé and Príncipe-Social Democratic Party (MLSTP-PSD). The first president was Miguel Trovoada of the Independent Democratic Action (ADI) party. However, in 1994 the MLSTP-PSD was just short of a legislative majority and formed a coalition with the Democratic Convergence Party-Reflection Group (PCD-GR). This began the period of cohabitation. Indeed, this period only ended in 2001. In the meantime, President Trovoada was re-elected in 1996 and the MLSTP-PSD did well enough at the 1998 Assembly election to form another coalition or a single-party minority government. So, in Sao Tome the mid-term factor was particularly important in creating the opportunity for cohabitation.

The first cycle of cohabitation ended with the election of Fradique de Menezes of the ADI in 2001. There was an ADI minority government for a while and then the president’s new party, Force for Change Democratic Movement-Democratic Convergence Party (MDFM-PCD) was able to maintain the premiership after the 2002 legislative elections. However, by March 2004 cohabitation was back. The MDFM was unable to maintain its position in government, or was unwilling to, and again the president’s party had no representation in cabinet. This period ended in June 2005, but in a previous posting I hinted that Sao Tome may be on the verge of another period of cohabitation, though because of early dissolutions the presidential and parliamentary cycles are now almost synchronised.

In total, Sao Tome has experienced more than 7 years of cohabitation by my reckoning since 1990.

In Mongolia, the prevalence of cohabitation has been largely caused by a two-block party system. Again, here semi-presidentialism dates back to 1990. In 1992 the Mongol People's Revolutionary Party (MAKN) won the legislative election. However, in 1993 President Ochirbat was re-elected under the banner of the Mongolian National Democratic Party (MUAN) against the MAKN candidate. When the MUAN won the legislative election in 1996 cohabitation ended. However, in 1997 the MAKN won the presidency and cohabitation began again only ending in 2000 when the MAKN won the legislative elections of that year.

Since this time there has been no repeat of cohabitation. So, there has been slightly less than 6.5 years of cohabitation in Mongolia since 1990. One of the characteristics of the Mongolian party system in recent years has been the breakdown of the two-block party system. The formation of new parties may make coalition-building more difficult but it may also reduce the prospect of cohabitation if the president’s party can position itself to be a necessary coalition partner even if it ‘loses’ a parliamentary election.