Republicans are forcing him to call it a mandate. Therefore it is.
By refusing to compromise, by not working with Obama and trying to block everything he does, the Democrats are forced to simply cram everything they can up the canoes of the Tea Party. They do not want their positions considered unless they get it all, which leaves a reasonable person nothing else to do.
If you're building a fence, say, and your neighbor refuses to consult with you, talk about type, height, style, or placement you about have to just put up what you want. Not much else to do.