The chairman of the panel that examined the nation’s security before Sept. 11, 2001 and the aftermath of the terrorist attacks announced Monday he was endorsing John McCain — and not former New York Mayor Rudy Giuliani — for president.

Former New Jersey Gov. Thomas Kean, a Republican like Giuliani and McCain, said the Arizona senator’s blend of congressional, military and foreign affairs experience left him the best equipped of the GOP candidates to serve in the White House.

Both on the campaign trail and in his new TV ads, Giuliani — who was mayor during the 9/11 attacks — has said his executive and crisis management skills make him the most qualified.

“In the history of our nation, a mere handful of senators have exerted a greater influence over free men and free women than even some presidents of the United States. John McCain has been one of those senators, and he has tremendous respect throughout the world,” Kean said at Logan International Airport, where the two jetliners that felled the World Trade Center were hijacked.

Kean also credited McCain with unmitigated support for the 9/11 panel’s 41 safety recommendations, as well as a post-attack overhaul of the nation’s intelligence services. Kean chaired the panel and former Rep. Lee Hamilton, D-Ind., was vice chairman.

“To the extent that we’ve been less vulnerable to attacks that we suffered on 9/11, it’s in a large part due to the extraordinary leadership of John McCain,” the former governor said.

McCain reveled in the endorsement, noting Kean joins a group of supporters that also includes former Homeland Security Secretary Tom Ridge and four former secretaries of state.

The timing also was politically potent. In a new ad that started airing Monday, Giuliani says: “I’ve been tested in a way in which the American people can look to me. They’re not going to find perfection, but they’re going to find somebody who has dealt with crisis almost on a regular basis and has had results.”

The former mayor’s campaign noted Giuliani has been endorsed by Kean’s son, New Jersey state Sen. Tom Kean Jr., who tried unsuccessfully last year in a bid for U.S. Senate.

Giuliani told reporters in Mission, Texas, that the elder Kean “has a right to endorse anybody he wants.” Giuliani added: “There are a lot of Republicans, I’m not going to get all the votes or all the endorsements.”

Kean twice refused to say whether he felt Giuliani was justified in citing his 9/11 experience to cast himself as the most qualified GOP presidential contender.

“I didn’t come here and wouldn’t criticize Mayor Giuliani,” Kean said. “I think the Republican Party this year is fortunate to have a number of good candidates. I just happen to feel that with this world we live in, with the dangers abroad, all around us, and the dangers here at home, that we need the very best. And the very best, I believe, is John McCain.”

Giuliani was widely criticized for locating the city’s emergency center in 7 World Trade Center, a building that contained thousands of gallons of diesel fuel when it collapsed after the terrorist attack.

Giuliani’s record as mayor drew close scrutiny and some criticism from the Sept. 11 Commission. Questions were raised about the failure of the Giuliani administration to provide the World Trade Center’s first responders with adequate radios, a long-standing complaint from relatives of the firefighters killed when the twin towers collapsed. The commission noted the firefighters at the World Trade Center were using the same ineffective radios employed by the first responders to the 1993 terrorist attack on the trade center.