A commenter in a below thread had these very worthwhile insights:

Pete, why do you prefer Mitch Daniels to Thune and Pence? Daniels may be great on fiscal and economic issues (which, I'll grant you, are of greatest salience now), but he has a demonstrated tin ear for dealing with hot button issues and, having watched a speech of his, he seems to me unlikely to appeal to ordinary voters, either in the base or in the general electorate. From what I've read, other than on money issues, he seems to be an unimaginative, uncharismatic, standard issue RINO/mainstream Republican. Also, can he address foreign policy or national security with any authority? In sum, he strikes me as well-suited for a governorship, but not for the presidency.

I think this is a very plausible interpretation of the problems that a Daniels presidential campaign might face and I would further add that Daniels' flirtation with a VAT would also be a problem.  That is why I think Thune or Pence are more likely to emerge from the pack.  That isn't how I want it to be, but it is how I see it.  Some points,

1.  Daniels is a standard social conservative on issues like abortion/gay marriage/Second Amendment.  He is no RINO. 

2.  Daniels' record of maintaining an acceptable record of public services while keeping spending under control is an important strategic advantage.  It gives him some credibility when talking about cutting the deficit and reforming government, while allowing him to point to a record to help parry accusations that he will starve Grandma.

3.  His health care policies begin to offer a plausible alternative to Obamacare that increases worker take home pay, decreases government costs, maintains care, and begins to reform the expensive and dysfunctional Medicaid program.  The fact that these policies were actually implemented is a huge advantage because he would not be offering purely speculative benefits.

4.  I would not underestimate Daniels as a speaker.  He was a former George W. Bush functionary who outperformed the Republican presidential nominee by 20% in a year when Bush's job approval ratings were in the mid-to-low 30s.  He is governor of a state with an unemployment rate over 10%, but his job approval rating is around 70%.  He doesn't project good humor like Huckabee or charisma like Rubio, but someone is liking what he is saying.  I know Indiana isn't America writ small, but on a national election level, it leans Republican less than does Mike Pence's congressional district, Huckabee's Arkansas, or Thune's South Dakota.  He has a way of talking about economic issues in a way that seems honest, relevant and temperate.  I'm not sure that it translates well in the context of a presidential campaign, but I'm not assuming it doesn't.

5.  Daniels would of course need policy answers on foreign and defense policy.

6.  I think that Pence, in his rhetoric, record and policy preferences is more in tune with a larger fraction of Republican primary voters than any other candidate.  As he gets better known, I think he has a lot of room to gain from voters who identify themselves as Tea Party supporters (he is at least as good as any other candidate on both the social and economic issues) and from more establishment Republicans who might think that Palin and Huckabee have electability issues.

7.  I take back none of my concerns about Pence as a general election candidate and as a President.

8.  John Thune is an interesting case.  There is some evidence he can play in the big leagues.  Beating Tom Daschle (even in a right-leaning state in a right-leaning year) was pretty impressive.  He could dig into Romney's establishment/basically conservative enough support.  Ramesh Ponnuru noted that Thune does not seem to have distinguished himself in six years as a Senator.  I've seen him on tv a couple of times.  He could be a vessel for a lowest common denominator conservative candidacy.