Obama has always been protestant if he is religious at all - maybe he attended chapel just for political reasons. He certainly left it for political reasons, and has wandered around various protestant sects since.
Afaik he has never set foot in a catholic church, except perhaps at catholic funerals he has to attend.
Yes, he has made a gamble, and this may be the one which will cause enough people to vote for Romney. There are other reasons for voting for Romney - particularly his abilities with his own and government money. However, the employment rate has just gone up, so maybe Romney will not have such a hold on economic matters come election time if the economy and the job scene keeps improving.
There are a lot of factors involved, and forcing religious people to act against their beliefs is a big one of them. If I lived in the USA I'd be a Democrat but come the election I'd be seriously thinking of voting for Mitt (though I'd vote Democrat for the local rep and senator). It's such a pity he's a Republican, the most appalling political party I know of (sometimes bordering on evil, with lies and some of its political activity).
I'd jot down pros/cons for both presidential candidates in November.