He was an effective, tireless cheerleader for Obama during the 2012 campaign, an effort in line with what he surely deemed best for the country. But it may have been best for Hillary in 2016, too. Had Obama lost, the Democratic nominee in the coming presidential election would be facing a Republican incumbent. Besides, Bill deftly kindled Clinton nostalgia, reminding people of a more prosperous era.

But the calculus for him over the coming years is much, much more complicated. If Obama doesn’t recover, if there are more fumbles and if Hillary formally decides that she’d like to carry the ball next, Bill’s best approach may be cheerleading mingled with fault finding, and the current president may be faced with a former president whose tangle of motives is unlike any that other former presidents possessed.

At the same time, Bill can’t be too vocal, too vivid. Exposure has risks, evident in his divisive remarks about the South Carolina primary that Hillary lost to Obama in 2008.

And in precisely the way that he sometimes makes Obama seem tepid, he could outshine Hillary, inadvertently or not. A friend of mine who went to a public event of hers last week was blown away by how not blown away he was. Amid all of the Hillary hullabaloo, he’d forgotten that she’s no dynamo on the stump. Many Democrats overlook this, but not the ones whispering sweet encouragements in Elizabeth Warren’s ear. Part of what they see in Warren — and part of what they believe could make her a spoiler — is a sizzle that doesn’t come as naturally to Hillary.