Cain - He had (might still have) the chance to be a Ross Perot-style outsider/self-made businessman/populist technocrat while also being an authentic conservative. He had an excellent chance of winning over that fraction of the Republican primary electorate that is interested in conservative authenticity first while also being able to use his background as a businessman outsider to convince those voters that he was competent enough to be trusted with the presidency. Cain's approach was always going to wear thin eventually, but it has decayed faster than I expected. Part of it is that Cain is no Ross Perot, and not just in the size of his net worth. Perot was vague on the answers to the country's problems, but he was a blizzard of facts and charts on the problems themselves. I can't remember a thing he said, but he sure seemed to know what he was talking about on the national debt. This gave him (for a time) the air of an expert outsider who would clean up the mess made by the Washington political class. Cain mostly just reads from the same old script about how he is a problem solving businessman who will get advice from the right people and announce a solution sometime later. Maybe if Bachmann hadn't shown up to give him competition for that portion of the electorate looking for a (nonlibertarian) authentic conservative outsider, he would be doing better. Or maybe not. He won't get very far running as a problem solver if he can't solve the problem of sounding like he is using a line of bs to get through the debates.
Pawlenty - As an Evangelical, strongly pro-life, spending cutting two term governor of a Midwestern state, Pawlenty had an excellent chance to win support from both the part of the Republican electorate that is looking primarily for authentic conservatism and the part that is looking for (conservative-tinged) governing competence. It hasn't worked out that way. His public appearances are one disaster after another. His CPAC speeches treated his audiences like yokels. The moderators in both Republican debates have made him look bad. I caught a few minutes of Pawlenty of the O'Reilly Factor the other day. O'Reilly (who had previously derided Pawlenty as vanilla) asked Pawlenty out for a vanilla sundae with hot fudge. It was actually a shrewd question by O'Reilly, in that there isn't an obvious answer that doesn't make one look like either a weakling or a jerk. I still don't know what I would have said. Pawlenty responded with his common line about not running for comedian-in-chief and rebuffed O'Reilly. It was a weirdly nonresponsive answer. O'Reilly had invited him out for ice cream, not to do set at the Comedy Store. There was probably some way to make Pawlenty's response seem principled, but he not only seemed stiff, his answer was so obviously scripted (it was obviously his stock answer to any question about being boring etc.) that he seemed phony too. I want to like Pawlenty (he would probably get my vote if I had to cast a ballot today), but he isn't showing that he can play the game at this level.
Bachmann - She did well in the first debate. As Matt Taibbi pointed out in his otherwise venomous profile, the people who mock her are among her greatest political assets. Every time liberal blogs put together pictures of Bachmann with her mouth wide open so that she looks stupid and crazy, they set expectations that she can easily surpass and they encourage conservatives to choose a side while making it an easy choice. And it works out all the better for her when she shows up as a politician of well above average intelligence and work ethic because it is a big surprise to many. She has travelled around the country and knows her audience. Unlike Pawlenty, she knows that being the first to file a bill repeal Obamacare is a better way to signal conservative authenticity than inviting conservatives to take inspiration from an act of suspected spousal battery. She speaks social conservatism as a first language. She knows how to play to the crowd, but she doesn't come across like she is pandering in the sense of being willing to say things she doesn't believe. I don't know why this hasn't gotten more play, but one of the reasons she did well in the debate (and I think her performance was somewhat overrated) was because she worked at it. She very probably wouldn't be a good general election candidate. I doubt her appeal will prove broad enough to win the Republican presidential nomination. Her biography and affect are appealing to someone looking for an authentically conservative outsider, but less well for those looking primarily for a chief executive.