DES MOINES, Iowa — Jeb Bush is preparing to embark on an experiment in presidential politics: delegating many of the nuts-and-bolts tasks of seeking the White House to a separate political organization that can raise unlimited amounts of campaign cash. The concept, in development for months as the former Florida governor has raised tens of millions of dollars for his Right to Rise super PAC, would endow that organization not just with advertising on Bush’s behalf, but with many of the duties typically conducted by a campaign. Should Bush move ahead as his team intends, it is possible that for the first time a super PAC created to support a single candidate would spend more than the candidate’s campaign itself — at least through the primaries.