Are independent, nonprofit groups that receive and distribute funds to influence the nomination, election, and/or defeat of a candidate.

The answer is 527 committees
The members of this commitees are exclusively taken from each party involved during the election.
the number 527 come from the fact that their finace are regulated under the sectionn 527  of thhe united states internal revenue code

527 Committees are tax-exempt and often consist of groups that have a specific political leaning or special interests. While they may not directly advocate for specific candidates, they can influence the public on specific issues.