Political parties have become an important part of the politics of almost every country, as modern party organizations have developed and spread around the world over the past few centuries. It is extremely rare for a country not to have political parties. Some countries have only one political party, while others have several. Parties are important in the politics of autocracies and democracies, although democracies generally have more political parties than autocracies. Autocracies often have a single party governing the country, and some political scientists view competition between two or more parties as an essential element of democracy. Political parties are often structured in the same way in different countries. Unlike umbrella parties, mass parties are funded by their members and rely on a large membership base. Moreover, mass parties prioritize voter mobilization and are more centralized than umbrella parties.   In a non-partisan system, there are no political parties, or political parties are not an important part of the political system. There are very few countries without political parties.  Political parties have different functions.
One of them is to promote the interests of their constituents. They also draw up party programmes. Citizens can join political parties and thus help shape the party`s programme. Political parties are essential institutions of democracy. By participating in elections, parties offer citizens a choice in governance and, when in opposition, they can hold governments to account. When citizens join political parties, volunteer, donate money and vote for their leaders, they are exercising their basic democratic rights. Citizen participation in political parties offers unique benefits, including the ability to influence political decisions, select and mobilize political leaders, and run for office. In some countries, however, political parties do not respect citizens` right to participate and are not accountable to voters. NDI supports the development of vibrant, accountable and inclusive multi-stakeholder systems that provide citizens with meaningful choices and opportunities for political participation.
The Institute`s work involves the exchange of knowledge and resources and aims to broaden the participation of marginalized groups, including: women, youth, ethnic and racial minorities, persons with disabilities, and sexual and gender minorities. NDI`s support extends to all party organizations, from rank-and-file party members to intermediate party officials and senior party leaders. The Institute is the only organisation officially represented in the four largest international groupings of political parties: the Centrist Democratic International, the Liberal International, the Socialist International and the Progressive Alliance. Through these networks, NDI promotes peer-to-peer exchange and consultation. The Institute also promotes constructive engagement between political parties and other institutions such as civil society, the media and electoral administration bodies. For example, parties can generally claim freedom of association, arguing that they, not the government, have the right to decide who can join or be expelled from the organization and how they manage their internal affairs. However, it is not always clear who the «political party» is under the law and who can assert First Amendment rights. The right of third parties to have access to ballots is a First Amendment issue in this area. In this photo, supporters of John Anderson march for the presidency Tuesday outside the Cleveland Convention Center and protest the debate between President Jimmy Carter and Republican candidate Ronald Reagan because Anderson was not invited to attend Public Music Hall in Cleveland, Ohio, on October 28, 1980. (AP Photo, used with permission from The Associated Press) However, in Clingman v. Beaver (2005), the court upheld a system of semi-closed primaries in Oklahoma that limited who could vote in a primary.
The Supreme Court held that the law did not interfere with the rights of the First Amendment parties to such an extent that it even required rigorous scrutiny. As a result of these decisions, it appears that political parties have rights of association, but it is not always clear who can assert them – party members or leaders. Before the development of mass political parties, elections were generally characterized by a much lower degree of competition, had communities so small that direct decision-making was possible, and held elections dominated by networks or individual cliques that could independently lead a candidate to victory. : 510 A political party brings together like-minded people. By participating in an election, parties hope to bring together as many of their members as possible in a representative body such as a parliament or a municipal council. At the same time, they try to hold as many positions as possible in the government or in the municipal or provincial executive. The term «catch-all party» was developed by German-American political scientist Otto Kirchheimer to describe parties that developed in the 1950s and 1960s through changes within mass parties.  : 165 The term «large tent party» may be used interchangeably. Kirchheimer characterized the shift from traditional mass parties to catch-all parties as a series of developments, including the «drastic reduction of the party`s ideological baggage» and the «devaluation of the role of the individual party member.»  By broadening their core ideologies to more open ideologies, catch-all parties seek to gain the support of a larger portion of the population. In addition, the role of members is reduced, as catch-all parties are partly funded by the state or by donations.
: 163-178 In Europe, the shift from Christian Democratic parties, organised around religion, to broader centre-right parties.  By the early 19th century, a number of countries had developed modern and stable party systems.