CHICAGO — Jeb Bush carefully attempted to open up distance between himself and his brother, President George W. Bush, in a much-anticipated foreign policy speech Wednesday, suggesting that in the Mideast, he would value stability even if that meant supporting autocrats rather than democratic forces.

In a speech to the Chicago Council on Global Affairs, Bush — widely viewed as the leading candidate for the Republican presidential nomination even though he has yet to formally announce his candidacy — also strongly defended the National Security Agency’s collection of records on Americans’ telephone calls, saying it was “hugely important” to protect the country against terrorism.

“For the life of me, I don’t understand” why the “debate has gotten off track” about the program, he said.

The defense of the NSA, and repeated references to the importance of “engagement” — a word he used in some form 22 times in a little more than an hour — drew a sharp line between the former Florida governor and potential rivals for the GOP nomination, particularly Sen. Rand Paul, who has denounced the NSA program and argued for reducing U.S. entanglements overseas.

But it was the distinctions Bush drew with his brother that did the most to start defining what a Jeb Bush policy might look like. Employing a line that his aides had widely advertised in advance, Bush said that while he admired his brother and their father, President George H.W. Bush, “I’m my own man, and my views are shaped by my own thinking and my own experiences.”

In the speech, he shed little light on what those “new approaches” might mean. Indeed, he completely avoided the most fraught part of his brother’s legacy, barely mentioning the word “Iraq,” except in an initial stumble in which he meant to say Iran.

However, Bush later broached the subject.

He defended his brother’s record, saying that “there were mistakes made in Iraq, for sure,” but that the troop “surge” in the final two years of the Bush presidency “was one of the most heroic acts of courage politically that — that any president’s done.”