DENVER — President Clinton forcefully endorsed Senator Obama’s bid for the White House today, telling delegates to the Democratic convention that Obama is “ready to lead America and restore American leadership in the world.”

Mr. Clinton pushed back on attacks — initiated by himself and his wife during the bitter primary campaign, and later taken up by Senator McCain, that Mr. Obama is ill prepared for the White House, especially on matters of national defense.

“With Joe Biden’s experience and wisdom, supporting Barack Obama’s proven understanding, insight, and good instincts, America will have the national security leadership we need,” Mr. Clinton said.

Mr. Clinton campaigned feverishly for his wife, Senator Clinton, in her long-fought primary battle against Mr. Obama, and took her loss hard. He had not spoken out as strongly in support of Mr. Obama since he clinched the nomination in June.

But today, he was unambiguous.

Jabbing a finger at thousands of cheering delegates, he declared: “I want all of you who supported her to vote for Barack Obama in November.”

Mr. Clinton was by turns funny, nostalgic, and wonkish, delving into issues like health care and pension benefits.

Mr. Clinton, ever mindful of himself, likened Mr. Obama’s presidential quest to his own bid for the presidency in 1992, when “Republicans said I was too young and too inexperienced to be commander in chief.”

“Sound familiar?” Mr. Clinton said. “It didn’t work in 1992, because we were on the right side of history. And it won’t work in 2008, because Barack Obama is on the right side of history.”

He allowed that the primary campaign had generated “so much heat it increased global warming.”

“In the end,” he said, “my candidate didn’t win. But I’m proud of the campaign she ran: She never quit on the people she stood up for, on the changes she pushed for, on the future she wants for all our children.”