CHICAGO • Former US president Barack Obama studiously avoided any mention of his successor Donald Trump or the assault on his own legacy as he returned to his adoptive home for his first public event since leaving the White House.

What might have been a moment for Mr Obama to challenge Mr Trump's wiretapping accusations, or to assail the Republican agenda, instead became a college seminar on how to engage with a new generation of young people - and urge them to participate in political life.

"The single most important thing I can do," Mr Obama told a student audience on Monday, is to "help in any way I can to prepare the next generation of leadership to take up the baton and to take their own crack at changing the world".

Avoiding Mr Trump was no accident. Mr Obama has decided - for now, at least - to steer clear of any criticism of his successor, in part out of gratitude that his predecessor, Mr George W. Bush, took that same approach. But Mr Obama and his advisers also have concluded that confronting Mr Trump now would be a political mistake.

If Mr Obama were to challenge President Trump directly, they believe, the former president would become a foil for Mr Trump's efforts to rally his supporters. That could end up helping Mr Trump enact policies Mr Obama opposes.

As a result, the session at the University of Chicago, where Mr Obama once taught constitutional law, was devoid of any Obama- Trump tension. Seated on a stage with six successful young people, Mr Obama was relaxed and casual, musing about his political life story and offering a few jokes.

"So, what's been going on while I've been gone?" he said, chuckling. Later, he hinted at the political climate by recalling his 2004 observation about there not being a "red" America or a "blue" America during his speech at the Democratic National Convention that year.

"That was an aspirational comment," he acknowledged, prompting laughter. "Obviously, it's not true when it comes to our politics and our civic life."

Mr Obama has spent the three months since Inauguration Day on an extended vacation even as his staff begins setting up an office in Washington and planning continues on his presidential library in Chicago. He is also starting to work on a memoir.

And he has begun what will be a series of public appearances. His next scheduled public event is a May 7 speech at the John F. Kennedy Presidential Library and Museum in Boston.

NYTIMES