Vice President Joe Biden said Thursday that the biggest factor in his decision on whether to run for president is whether he and his family “have the emotional energy to run.”

“The honest-to-God answer is, I just don’t know,” he said.

That deeply conflicted response was the first public articulation of a thought process he’s discussed until now only privately with top Democrats and close advisers. He gave no timetable for a decision.

The question came after a lecture in Atlanta, where Biden defended the Iran nuclear deal and discussed world affairs at the Ahavath Achim Synagogue.

“I’ll be straightforward with you. The most relevant factor in my decision is whether I and my family have the emotional energy to run,” Biden said. “Some people might think that is not appropriate. But unless I can go to my party and the American people and say that I am able to devote my whole heart and my whole soul to this endeavor, it would not be appropriate.”

He did not mention Hillary Clinton, the former secretary of state whose candidacy has faced mounting questions about her handling of classified information on a personal e-mail account, creating a possible opening for the vice president.

“And everybody talks about the other factors — the other people in the race, whether I can raise the money and whether I can put together an organization. That’s not the factor. The factor is, can I do it? Can my family undertake an arduous commitment that I would be proud to undertake under ordinary circumstances?”

Biden has been mourning the death of his son, Beau Biden, the former Delaware attorney general who was considering a race for governor before his death from brain cancer in May.

But it was a previous tragedy — the death of his first wife and daughter in a 1972 auto accident — that Biden mentioned Thursday. “I know from previous experience after my wife and daughter … there’s no way to put a timetable to it.

“If I can reach that conclusion that we can do it in a fashion that would still make it viable, I would not hesitate to do it,” he said. “But I have to be honest with you and everyone who’s come to me, I can’t look you straight in the eye and tell you I can do it. That’s as honest as I can be.”

Vice President Joe Biden speaks at the Ahavath Achim Synagogue in Atlanta, Thursday. Biden was making his remarks at the Fran Eizenstat and Eizenstat Family Annual Lecture. (Photo by Erik S. Lesser/European Pressphoto Agency)