A) nominating: A political party, typically through a public vote by citizens who identify with that party, will nominate candidates who run for public office under the banner of that party. One example is the Republican Primary election, in which Republican voters elected Donald Trump to be their nominee in the General Election against Hillary Clinton.
B) Informing and Activating: Political parties work to inform their constituents of issues that they value and believe other party members should value, and to encourage them to agree on the party position. One example is the evolution of the Democratic position on same-sex marriage, and the effort by the party to both energize and convince their voters on the issue and inform them of the details of the issue's current legal status.
C) Serving as a bonding agent. A political party serves as a bonding agent because it unites people of similar demographics, such as ethnicity, social status, or social values, under a united political banner. This can empower these groups and make their voice louder on the political stage. One example is the NRA's relationship with the Republican party.
D) Governing: Political parties' main function, ideally, is to govern. An example is Democrats and Republicans in government serving as elected members of Congress, and passing laws.
E) Serving as a Watchdog: The adversarial model of government, in which political parties compete for power and the furthering of their respective platforms, can have a positive watchdog effect. Their is accountability required of those in power, since unlawful activity could be caught by an opposing party. One example is the investigation of the Watergate scandal, led largely by Congressional Democrats, against the Republican Nixon Administration, which ultimately resulted in Nixon's resignation.
