The plan, code-named “Homeland Security,” seeks to try to neutralize two potentially grave but homegrown threats to Mr. Bush’s long-anticipated run for president: the likely challenge from a charismatic young Republican senator from Miami, Marco Rubio, who is expected to seek the Republican nomination himself, and a demographic drift within Florida that could doom Mr. Bush there in a fall campaign against a Democrat…

Mr. Bush’s next steps are clear, advisers said. He must prevent Mr. Rubio from building a credible operation in the state; make the case that as a Spanish speaker with a Mexican-born wife, he can overcome demographics that might otherwise favor the Democratic nominee; and, lastly, construct a robust fund-raising operation that can collect the tens of millions it would cost Mr. Bush to win Florida in a primary and general election.

Behind the scenes, those close to Mr. Bush are moving quickly to undermine Mr. Rubio. A close Bush ally, David Johnson, has taken over the state’s Republican Party as interim executive director and, in a blunt interview here, sought to discourage Mr. Rubio from entering the presidential race.

“I hope that is not going to happen,” Mr. Johnson said. “It’s going to cause a lot of problems in the state of Florida.”