I can tell you a bit about the communists in the Czech Republic. They have had some relative success in parliamentary and local council elections, and maintaining a minor but rather steady and notable presence in the parliament, but have had basically no power when it comes to forming governments, not even as potential coalition partners.

The Communist Party of Bohemia and Moravia (KSČM), that is the communist party currently active in the Czech Republic, is indeed the Communist Party of Czechoslovakia (KSČ), or rather a constituent part thereof. The KSČ survived the democratic revolution of 1989, but in 1990 reorganized itself, and in addition to the already existing Slovak wing of the party, a Czech one was formed. These two regional divisions would form the party proper until the dissolution of Czechoslovakia, and the Czech one – the KSČM – exists to this day.

While by no means the authoritarian force of 1945–1989, they have not really transformed into a social democratic party as we understand that term today. Their political programme clearly describes itself as stemming from marxist theory, and they have explicitly named "the very existence of capitalism" as the "root of the mounting problems facing the world", and some of their members have been rather vocal about not being particularly reformed, including gems such as making light of the victims of the previous regime or playing down the intervention of Warsaw Pact troops in 1968. The social democratic position proper is represented, perhaps somewhat obviously, by the traditional Czech Social Democratic Party.

The communists have had a notable presence in the Czech parliament ever since the Velvet Revolution. In fact, in the four elections between 1992 and 2002 they have not dropped below ten percent, and 2002 actually saw their greatest election success with 18.51% of the votes, translating into 41 out of the 200 seats in the chamber of deputies. In 2006 and 2010 they only secured 12.81 and 11.27 percent respectively, but in the 2013 election they had gained 14.91% votes and 33 seats, their third best result in the history of a democratic Czech Republic.

You might have noticed the 2013 election year as (literally) odd, and it was exactly that, an early election following a series of events and scandals which absolutely rocked Czech politics. The political suicide of the center-right Civic Democrats, and the subsequent meteoric rise of the populist but otherwise difficult to describe ANO, have massively shifted the traditional landscape of the two big boys – the Civic Democrats and the Social Democrats – vying for power.

These turbulent events might have helped the slight rise in the communists' fortunes, as very recent polls put them around the 11–12% mark again. As a sidenote, in 2012 they have also had some success in the regional council elections, however, not only are those a different matter altogether due to their local nature, but perhaps even more importantly, at that time ANO were not yet involved, a situation that will change in a few short months in the upcoming election.

However, although often finishing third – a distant third, but still – in several elections, the communists have not been successful at all as genuine government partners. They have not been a part of a single coalition government, and basically spent the last twenty five years in opposition or as occasional pragmatic and short term allies at best. Their seats or tacit support have come handy on particular issues at times, and a couple of past governments have toyed with the idea of more closely aligning with them for a more secure base of votes but nothing ultimately came out of it.