Graft = Practices, esp. bribery, used to secure illicit gains in politics or business; corruption.
Lobbying = Seek to influence (a politician or public official) on an issue.
There have been very public accounts of both graft and lobbying in recent news coverage. There is also no other explanation for a candidate to spend hundreds of millions of dollars (donated or not) running for an office that pays $400k annually for not more than 4 years.
Let's also suggest a detailed audit of exactly where our $16 trillion was spent.