In the public funding system for presidential elections,

O presidential candidates are prohibited from raising private dollars for their election after the national party conventions.
O presidential candidates can receive federal funding for their campaigns provided they finish among the top three candidates in the New Hampshire primary.
O third-party candidates receive federal funds to encourage them to run against the privately funded Democratic and Republican nominees.
O the federal government provides funds to candidates in exchange for the candidates' agreeing to restrictions on fund-raising from private donors.