A political party is an alliance between interest groups. They appear in countries that have elections, and are absent in countries without them, differentiating the experience and mechanics of democracies from autocracies.
Interest groups band together into political parties for the purposes of elections and forming governments. There are many dynamic names and conditions that work to create plausible and flavourful parties no matter which direction the player chooses to guide their country.
Party types
There are 11 potential political parties that interest groups can join. Many of these parties are aligned primarily around a particular interest group's core ideologies, which other IG's may join under the right circumstances. Other parties are aligned more strongly with leader Ideologies that emerge throughout the game, such as the Communist party and the Radical party.
At any given time, any combination of these parties might exist or not exist. Parties emerge and disband dynamically, so the political landscape can be very different between countries and playthroughs.
The following parties can emerge throughout the course of the game:
- The Agrarian party
- The Anarchist Society
- The Communist party
- The Conservative party
- The Fascist party
- The Free Trade party
- The Liberal party
- The Military party
- The Radical party
- The Religious party
- The Social Democratic party
The Liberal party, for instance, is the natural home of the intelligentsia due to their liberal ideology, but they may be swayed towards other parties under various circumstances.
Note: Each of these parties has a variety of dynamic names based on national, cultural, and religious factors. For example, in 
大不列颠 the Conservative party is localized as the Tories, while in the 
美利坚 they are known as the Democratic party.
Party formation
Interest groups (IG's) may join a political party if they are not marginalized and if their country has any of the laws that allow elections.
Which political party an interest group will join is determined by a wide variety of factors, some of which are:
- IG's with the Republican, Radical, Market Liberal, or Reformer leader ideologies are much more likely to join the Liberal party.
- The
industrialists are more likely to be drawn towards the Conservative party if the country has public healthcare or schools, or when voting laws allow the lower strata to vote. - Weaker IG's might join the Agrarian party alongside the
rural folk in a push to abolish Serfdom. Scandinavian countries are much more likely to develop an Agrarian party. - In a Council Republic, IG's led by anarchist leaders might leave the Communist party if the country's ruler is a vanguardist.
- When an IG with a Fascist leader becomes powerful, weaker conservative IG's might join the Fascist party in a bid to retain their political relevance.
- If a powerful IG has a Social Democratic leader, weaker leftist IG's may fall in line behind their more moderate cousins. Likewise, weaker Social Democrats might join a stronger Communist party.
Just as parties ally together when they form a government, they also share their momentum in elections, which determines their votes. During the election campaign period (which lasts 6 months before the final votes are cast), the player is likely to get events relating to the various party's campaign efforts that can have a major impact on momentum. These events are inspired by the campaigns and scandals of the period.
If, for instance, the fascist leader of the 
petite bourgeoisie joins the Conservative party and is caught up in a political scandal, the whole party suffers the electoral consequences. On the other hand, as the 
Landowners begin to lose their political relevance in an increasingly industrialized economy they might cling to relevance by attaching themselves to the rising Fascist party, who may bring them political power from the votes the whole party gains in the election.
Bloc
Interest groups must be added or removed from government as a single bloc, which means that the player will need to make strategic decisions about the makeup of their government and deal with the consequences. For example, the Liberal party may contain both the 
intelligentsia and the industrialists, who will both back plans to move toward a free market economy but diverge on the issue of child labor.
Sometimes an opposition interest group might decide that it wants to join a party currently in government (or vice versa). In this circumstance, the interest group will leave their old party and be marked as "wanting to join" their new party. This won't force any interest group into or out of government, but if the player decide to reform their government under these circumstances then they must treat that interest group as being a member of the new party, bringing them into or out of government as a single bloc.