Individual contributions are the primary source of funding for political parties in the United States. These contributions can come from a variety of sources, including individuals, political action committees (PACs), and labor unions.

Hard money contributions are those that are subject to federal campaign finance laws and can be used for a variety of purposes, including paying for campaign expenses and party-building activities. Soft money contributions are those that are not subject to federal campaign finance laws and can only be used for certain purposes, such as voter registration and get-out-the-vote efforts.

PACs can only accept contributions from individuals, while super PACs can accept contributions from corporations and labor unions. PACs are subject to federal campaign finance laws, while super PACs are not. PACs can only spend money on candidate campaigns, while super PACs can spend money on independent expenditures.

The Federal Election Commission (FEC) is an independent regulatory agency that enforces federal campaign finance laws. The FEC has the authority to investigate violations of campaign finance laws, impose fines, and refer cases for criminal prosecution.

The Bipartisan Campaign Reform Act (BCRA) of 2002 is a law that reformed the way political parties raise and spend money. The BCRA banned soft money contributions, increased the limits on individual contributions, and created new rules for the disclosure of campaign finance information.

The Citizens United v. Federal Election Commission (FEC) case is a Supreme Court case that struck down the ban on corporate and labor union contributions to political parties. The Court held that the ban violated the First Amendment's guarantee of freedom of speech.

The potential consequences of the Citizens United decision include increased spending on political campaigns, more influence for wealthy donors in politics, and a decline in the influence of political parties.

Some of the proposals for reforming party finance include public funding of elections, a ban on corporate and labor union contributions to political parties, and limits on individual contributions to political parties.

The challenges to reforming party finance include the influence of wealthy donors, the role of money in politics, and the First Amendment's guarantee of freedom of speech.

The future of party finance is uncertain. It is possible that the current system will continue, that there will be incremental reform, or that there will be major reform. It is also possible that the Supreme Court will overturn the Citizens United decision, which would have a significant impact on party finance.