Perhaps you need some remedial MSM training. I mean, you seem to be almost absolutely clueless? The mainstream media folks were so desperate in 2008 to turn the campaign into a referendum on race; they somehow thought if only a partial black POTUS was elected, it'd "prove" to the world that "See, we're not a nation of racists, after all, as our campus profs have been preaching week in, week out about 'white privilege.'"
To the credit of the McCain campaign, they kept a lot of that nonsense out of the news segments and print of the MSM.
Now, insert Mythster Romney in place of McCain, and how would that have egged on that already desperate MSM? Why, the MSM would have turned the whole thing into an all-out, full-scale referendum on racism! And the door-opener to that? Because the Republican candidate, had it been Mythster Romney, would have focused on what tight associations he had up through age 30.
You just can't get around the fact that at age 30, Romney was a priestholding, tithing member of a church that was still (at that time) denying priestholder status to blacks. Why, that would have been the daily banner headline all Fall long. While Romney would have done better vs. Hillary than 'O' -- "better" doesn't mean winning.
...suffice it to say that Romney was the only one with a snowballs chance who could speak to both conservatives ... and the middle...and women... and some youth.... which is exactly what it takes to win. [edit35]
Already mention was made by other posters about "anti-Mormon" sentiment. But Gallup polling from 2 years ago showed that conservatives were 9% more likely to vote for an LDS POTUS candidate than liberals -- and 11% more likely to vote for an LDS candidate than moderates.
There's no way you can get around that. Nationally speaking, Romney's greatest appeal, vote block wise, was actually to conservatives (despite his waffling social issues stances). He certainly wasn't going to get the vote of liberals.
That left moderates -- the group least likely to vote for a Mormon, said Gallup! [Come on, use your head! Who pulled McCain thru the Republican primaries...it wasn't conservatives -- 'twas moderates]. Moderates didn't vote for Romney in the primaries; and independent moderates are part of the largest "no we're not going to vote for a Mormon POTUS" crowd.