Before dropping out of the presidential race, John Edwards secured a private commitment from Barack Obama and Hillary Clinton that they'd undertake a poverty tour during the general election as the Democratic nominee, according to multiple sources familiar with the talks.

The vows to undertake a poverty tour -- which were confirmed to me by three former top advisers to Edwards -- went considerably farther than what has been publicly known until now about what the two Dems promised Edwards they'd do on poverty. During his drop-out speech last January, Edwards only said that the two Dems had "both pledged" to "make ending poverty central to their campaign."

An actual poverty tour, by contrast, would be a specific, protracted undertaking, possibly with Edwards himself, a possibility that came up in the private talks. Such a tour could be a major media event.

Now that Obama is on his way to becoming the nominee, the private promise is particularly relevant, because it raises the question of whether Obama will honor the commitment Edwards advisers say he (and Hillary) made.

This could require Obama to make a commitment of several days during a hard-fought general election, because Edwards specifically secured a commitment that it be a few days long, one top adviser said.

"Edwards was trying to think of ways to specifically hold them accountable," said another former top Edwards adviser. "It's easy for a Democrat to say, `Sure, I'll make poverty central to my campaign.' A poverty tour was something he felt would be really powerful with the spotlight of the general election, and it was a tangible, real thing he could ask them to commit to."

Matthew Nelson, a spokesperson for Edwards, declined to comment on the talks about the poverty tour, saying that Edwards "does not publicly discuss private conversations."

It's unclear whether Edwards himself explicitly insisted that he accompany the eventual nominee on the tour. But the possibility was discussed, according to two sources familiar with the talks. Indeed, one of the Edwards advisers said that Hillary and Edwards talked in some detail about how the two of them could do such a thing and "make it new and interesting."

But it's Obama who's now on his way to winning. The Obama campaign (and the Hillary camp) declined to comment on any aspect of this story.

Another of the advisers said that Edwards had secured a commitment that he'd accompany the tour. "It was a specific number of days on the road together, putting poverty front and center -- it would be with him," this adviser said. "He got them both to agree to this. He was really excited."