TALLAHASSEE, Fla. — The political apparatus surrounding former Gov. Jeb Bush, determined to avoid embarrassment in a state that has vexed his party and family in national elections, is plotting a vast operation aimed at turning Florida into a bulwark for his presidential campaign, according to dozens of interviews.

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.

The Bush effort in Florida, where Barack Obama prevailed in the last two elections, will pour enormous resources and energy over the next year into a state that many thought Mr. Bush, its governor from 1999 to 2007, would be able to count on as a bedrock of support.

“Without Florida,” said Bob Martinez, a longtime Bush friend and a former governor of Florida himself, “he knows it would be hard to make the numbers work.”