But she said that at the beginning of January, she began to discuss her departure with President Obama.
"And I went back to him in early March and said, 'You know, I'm really optimistic we're gonna meet the targets and the enrollment is good. While the site is working well, I think once we finish this first chapter you really should begin to look for the next secretary who can be here through the end of your term.' And that really wasn't a commitment I was willing to make," she said.
"I made it pretty clear that that really wasn't an option, to stay on. I mean, it was fair to either commit till January of 2017 or leave with enough time that he would get a strong competent leader."
Sebelius, who was in charge of implementing Obamacare, said that the law has ultimately been successful, despite the glitchy rollout. But she did speak about the low point for her.
"I would say that the eight weeks where the site was not functioning well for the vast majority of people was a pretty dismal time," she said. "But having failed once -- at the front of October-- the first of December became a critical juncture of other-- It was going to meet the expectations the second time around. I knew we didn't have a third time around. So, it was-- that was a pretty-- a pretty scary date."