Confabulated Knowledge

Romney, the republican nominee for president, has spent a lot of money in my state... Every hour there is around 15-20 commercials promoting him. One of these commercials caught my attention. One where Romney's advertising campaign stated that Barrack Obama had spread "Vicious lies" against fellow democrat Hillary Clinton.

This peaked my curiosity. The political world can be extremely biased so its difficult to find a straight answer, thus is why i'm asking here, out of the thousands of people who visit this site, one of them must have a competent answer right?

What would Barrack Obama gain from "attacking" Hillary Clinton? How would that further his cause to solidify himself as a good president and worthy of re-election? Or had perhaps Hillary struck first, and Obama was merely defending himself? Obviously Romney would take advantage of any opportunity he has to discredit Obama... But is he taking Clinton's words out of context?

Intelligent answers appreciated.