Seeking Political Office:
Candidates running for the U.S. House, Senate or the Presidency, " must register with the FEC once you (or persons acting on your behalf) receive contributions or make expenditures in excess of $5,000. Within 15 days of reaching that $5,000 threshold, you must file a Statement of Candidacy (FEC Form 2 [PDF]; Instructions [PDF]) authorizing a principal campaign committee to raise and spend funds on your behalf. Within 10 days of that filing, your principal campaign committee must submit a Statement of Organization (FEC Form 1 [PDF]; Instructions [PDF]). For additional information for new or incumbent campaigns, see this Record article on Preparing for the Next Election."
(Extracted from http://www.fec.gov/ans/answers_candidate.shtml)