Candidates who are considering a run for office can form legal organizations known as exploratory committees. Presidential office-seekers in particular use this practice, though candidates for House and Senate may do so as well. The maneuver is popular because it allows a candidate to raise money under less stringent rules than those that apply once he or she is an official candidate, and may also get more news coverage (first by forming an exploratory committee, then by announcing a formal candidacy). Individuals wishing to form exploratory committees must files papers with the Federal Election Committee, which oversees their activity.
Federal Election Commission