On the surface of it, Romney shouldn’t have to give a Mormon speech any more than Obama should have to give a Muslim speech. ~Patrick Ruffini 
Except for the small matter that Obama isn’t a Muslim. The remarkable thing is that Obama has spoken more openly and directly about his experience living among Muslims and about his Muslim ancestors, while Romney has avoided discussing his religion whenever possible. The perceived connection between Obama and Islam is probably far more damaging to him than Romney’s Mormonism is (because public opposition to a Muslim presidential candidate is even greater), but he and his supporters keep talking up his time in Indonesia, apparently oblivious that every time someone mentions Indonesia and his great understanding of the “Islamic world” many voters hear, “Obama is a Muslim.” One tries in vain to explain to these people that he lived there, but did not actually convert. I attempted to explain the facts at a recent Thanksgiving gathering, but the Obama-is-a-Muslim meme is already becoming engrained. They know that he lived in some Muslim country “over there” and that is enough to confirm their worst suspicions.
Besides, wo we really think, given the state of affairs and the public mood, that if a presidential candidate were a Muslim that he wouldn’t have to address it publicly in some way? Of course he would. The perception that both candidates belong to non-Christian religions are clearly political liabilities, as poll after poll on Muslim and Mormon presidential candidates shows, but the difference is that the Obama-is-a-Muslim meme is a lie, while Romney is something like a fifth-generation Mormon and proud of it. Obama shouldn’t have to give a major speech to debunk unfounded rumours. If Romney wants to be competitive, not just in the primaries but also for the general election, he needs to confront the reality, troubling as he and others may find it, that at least a quarter of the electorate is currently opposed to considering voting for him for no other reason than his religion. As polling on this reveals, this sentiment is more or less evenly spread across the political spectrum.
Ruffini adds in an update:
The anti-Mormon bigots and the anti-Muslim rumormongers seem to exist on about the same level — and neither candidate should let these fringe elements define their campaign.
Well, if you want to define somewhere between 25-43%  of the electorate as “fringe elements,” I guess you can do so, but I’m not sure how someone wins an election by ignoring such huge levels of built-in opposition.