The two men effectively became enemies four years ago, when the political differences between then-opponents Hillary Clinton and Barack Obama grew personal. And no one appeared to take every slight more personally than Mr. Clinton, whose frustration that a man he saw as a political lightweight was successfully challenging his wife in the Democratic primary hardened into barely-disguised animosity.
The relationship has come a long way since then. That's due in part to Mr. Obama's decision to reach out to the former president (the two men bonded over golf last September), partly because he tapped Mrs. Clinton to be Secretary of State, partly because the two men are now both members of a very exclusive club, and partly because it is to the benefit of both to move on from their past differences. They may not be particularly close personally - the introverted Mr. Obama was never likely to develop a strong rapport with the glad-handing extrovert who preceded him - but they've managed to develop a solid bond since the relationship thawed in 2010. Solid enough, in fact, that Mr. Clinton now seems nearly as enthusiastic about Mr. Obama winning reelection as the president himself.
"2008 was obviously directly impacted by the primary campaign, and there was some sorting out that had to happen after that campaign, but I think the relationship has really blossomed since then," said Mike McCurry, who was Mr. Clinton's press secretary for four years. "They talk to each other, I think, pretty regularly - there's a relationship that's grown and matured in the last two years."
"It's a very strong and healthy relationship, I think it sort of beings at the fact that there's only a limited amount of people who have actually had that job," added Democratic political consultant Chris Lehane, who was Al Gore's press secretary in the Clinton White House.
On Wednesday night, Mr. Clinton will deliver what is widely seen as the most important speech of the 2012 Democratic National Convention outside Mr. Obama's own, when Mr. Clinton will place Mr. Obama's name in nomination. Michael Waldman, who spent four years as Mr. Clinton's director of speechwriting in the White House, said one of the former president's most important tasks will be to engage voters prone to tuning out politics on a policy level.
"He is incredibly good at explaining policy in human terms and drawing contrasts between Democratic and Republican approaches in a way that is sharp but not shrill," said Waldman.
One of the biggest advantages to giving Mr. Clinton a prime-time slot is that he takes Americans back to a time when they were relatively well off -- and the nation was running a surplus -- under a Democratic president.
"He reminds the nation, and particularly independent and swing voters, that things were pretty prosperous in the 1990s because he rejected a lot of the Republican policies that are being advanced now," said McCurry. "He instantly evokes the memories of when things were a little better for Americans, and can credential Obama as a guy who will make the touch choices."
An aide to Mr. Clinton tells CBS News that the former president has been working on his speech for weeks -- and that he wrote almost all of it himself. Asked what to expect from in Mr. Clinton's remarks, a senior Obama campaign official pointed to an ad featuring the former president entitled "clear choice."