My first choice has always been Romney. I had strong leanings towards Cain to start with, and I considered Perry, but I thought they were not up to Romney. I look at their records, and accomplishments. Of the two really left in the running, they both have good and bad in their closets, but one has far less bad than the other, in my opinion, with far more accomplishments.
Newt Gingrich has too much baggage. He resigned from congress in disgrace, I remember the public outcry over his ethics charges. He is just too pompous, and self centered. He keeps trying to live in the shadow of Ronald Reagan. It's insulting after what he did back then.
Romney has some great accomplishments on his record. Not only has he had the experience of running a State Government, he is an accomplished businessman. He is a good troubleshooter, look at what he did for the Olympics. He took a failing project and turned it around. I remember reading about all the problems with the Olympics, how it was a failing proposition, and Utah was looking at cancelling the entire program. The people running it had bungled the whole program, it was out of funds, and supporters had pulled out. At the time I thought what an embarrassment to the nation. Entered Romney, he got new sponsors, Romney pulled everything together. Opening night I was doubtful it would live up to expectations, but it turned out great, far beyond expectations. All on account of Mitt Romney.
There you have my reasons, Santorum in my view was never in the running. I never thought him at all as a viable candidate. He and the other guy need to go ahead and drop out.