If Democrats are against something, i.e. the Supreme Court ruling, you can rest assured it is for some self-serving reason they are misrepresenting to the public with the complicity of their tools in the media.
So Obama—a one time professor of Constitutional law—told congress to pass a law which would overturn a Supreme Court decision! Good God, even I know better than that! This clown taught law like I taught nuclear physics!
My theory is that the Dems have a low opinion of their voters. The big money in campaigns go to emotional media productions. Dem voters are more ruled by emotion than Repubs and thus are highly susceptible to these kinds of last-minute ads. Repubs, being more logic or principle-minded, would be less persuaded by slick advertisements and emotional appeals. This, I think, accounts for some of the presumed unease Dems have with unfettered campaign spending.