President Bush has more than two years left in the White House, but planning is already under way to provide him security once he leaves.

The spending bill for the Homeland Security Department, which Bush recently signed into law, includes money to recruit, hire and train new Secret Service agents to work on the 2008 campaign trail. Those recruits subsequently will replace senior agents assigned to Bush when he becomes an ex-president.

The approach “allows for a smooth implementation of protection and transition of personnel without jeopardizing other critical program operations,” according to a Homeland Security budget report to Congress.

The report said Bush, like his father George H.W. Bush and former President Bill Clinton, is expected to be active and to travel overseas. But because of the war in Iraq and the ongoing terrorism threat, “the president’s post-presidency detail will require significantly more resources than are currently staffing other former presidents.”

The Homeland Security Department originally asked Congress for $5 million to pay for 17 agents associated with Bush’s post-presidency needs in 2008. Lawmakers added $11.5 million to cover those positions and for protecting presidential candidates.

The Secret Service declined to detail how the money would be split between tasks or to comment on plans for Bush’s post-presidency. “We don’t discuss how we do protection,” said spokeswoman Kim Bruce.

Under a 1994 law, the Secret Service detail for ex-presidents and their families lasts for 10 years. That protection can be extended if it appears there is still a threat. The law applies to presidents who took office after January 1997, meaning Clinton still gets lifetime protection.

Some former Secret Service officials and presidential scholars predict Congress eventually will reverse its decision to stop guarding former presidents for their entire lives.

“You’ll see that with 9/11 and the war we’re in and the memories of people going for decades, the Secret Service and Congress will have to change that and make it a lifetime (requirement) again,” said William Pickle, a 26-year Secret Service veteran who is now outgoing sergeant at arms for the U.S. Senate.

Congress ended the lifetime protection requirement after debating it for years. Lawmakers said they were troubled by the cost and noted that former President Richard Nixon dropped his Secret Service detail in 1985, nine years before his death.

“He didn’t feel the need to have it,” said Mark Updegrove, author of “Second Acts: Presidential Lives and Legacies After the White House,” a new history of ex-presidents’ activities. “He did so at a time when the world was a little quieter and the threats weren’t as abundant. … He inspired such passions that it was somewhat surprising.”

Updegrove said the Secret Service did not give lifetime protection to ex-presidents until after President John F. Kennedy’s assassination in 1963, when former presidents Herbert Hoover, Harry Truman and Dwight Eisenhower were still alive. He said Truman’s wife, Bess, initially resisted having “that level of intrusion in her life” until President Lyndon Johnson persuaded her to do so.

Since then, he said, former presidents have accepted the extra security.

“After a time, you become inured to the fact that you have this detail trailing you around,” Updegrove said.

At least one former president was the target of an assassination plot. When Bush’s father visited Kuwait in April 1993 to mark the victory over Iraq in the Persian Gulf War, Kuwaiti authorities arrested 17 people allegedly involved in a conspiracy to kill him using a car bomb.

Security levels for ex-presidents depend on various factors, such as where they travel and available intelligence about threats, former Secret Service agents said.

“More and more, the service doesn’t protect people based on position – they do it based on assessments, on the intelligence,” said John Enright, a veteran agent who guarded the elder Bush and Clinton, and who is now a Cranston, R.I., security consultant.