Does Brown hate Cameron and Osborne so much that he’d give up his job to defeat them?

Like Steve Richards in today’s Independent, I think it’s highly unlikely that Brown won’t remain Labour leader until the next election.  But Richards does spell out an alternative scenario which is news to me:

“It is still possible that Brown might go of his own accord before an election, without a new job offer. When things were going badly last time around, he told an ally that he felt guilty about what was happening to Labour under his watch. If he felt a Tory victory could be prevented by his departure he would consider going. I suspect that Brown would do anything to stop Cameron and Osborne securing power, including stepping down for a vote-winning alternative.”