Face the facts. He was elected twice, and by more the second time than the first. He won by a much wider margin the FIRST time against McCain - the 2nd time was comparatively closer
In 2008, it was something like 69 million for Obama, 59 million for McCain, with Obama winning about 192 more electoral votes
In 2012, it was something like 65 million for Obama, 60 million for Romney, with Obama winning about 106 more electoral votes
So by every general measure, Obama was elected by more the first time, not the second. (My numbers above are approximations and not the actual numbers, but they're directionally close).
Nothing was going to stop what happened in 2008. Had Romney run a more aggressive campaign and had he taken things a bit more seriously, he would have won. And while I can't prove it, it's my belief that if the election were held today (which it obviously won't be, so this is just spit-balling), Obama would lose.
Now I know how Democrats felt after 2004. George Bush was very beatable, but John Kerry was a terrible candidate.