My ranking...
1. Bush
2. Christie
3. Paul
4. Cruz
5. Perry
I voted for Cruz since I think he's undervalued on this forum. Read blogs like Redstate. Cruz is the darling among a lot of conservatives. Walker is really just a consensus candidate that isn't unacceptable to anyone...but he's SO BORING. But there are way too many charismatic candidates or candidates with strong niches (i.e. Paul with libertarians or Bush and Christie with moderates) for a consensus candidate to cut through the field.
Don't make the mistake of assuming "blogs like Redstate" mean anything. Republicans on the internet absolutely despised McCain and Romney in 2008/2012, and they still won anyway. Hell, Free Republic actually banned Romney supporters because they were "communist liberals" or something. That said, you may have a point he may be somewhat undervalued, simply because the field is so large it could only take a strong debate performance to propel him into a win in Iowa or South Carolina. And with a larger field, his small but loyal base is more powerful than it otherwise would be.
Oh I know...that's why I put him fourth...but maybe I should revise that top five...take out Perry?
I'm leaving out Carson I think he flops...at most he draws a few % here and there but no money and no organization.
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2012 Iowa Caucus: 25% Santorum, 25% Romney, 21% Paul, 13% Gingrich, 10% Perry, 5% Bachman.
There were four camps that mattered in the 2012 Iowa Caucus : Moderates (Romney), Libertarians (Paul), Social Conservatives (Santorum + Bachmann), and The Base (Gingrich + Perry).
Let's assume the camps in 2016 are: Moderates (Bush and Christie), Libertarians (Paul), Social Conservatives (Huckabee and Santorum), and The Base (Cruz, Walker, and Perry).
So 2016 Iowa Caucus Results:
Paul (21%) - Same as his father since its a crowded field. He's the only Libertarian and has no one cannibalizing his votes.
Bush (17%) - Able to bring in more money than anyone and leading in the aggregate of nationwide primary polling.
Huckabee (14%) - Has been doing well in polls for this state.
Walker (12%) - Gets some support from the base and some from the moderates. Midwesterner?
Cruz (12%) - Has a dedicated energized following. Memorable in the debates?
Perry (10%) - Does better in the debates than last time...but the same in the polls since its a crowded field.
Christie (8%) - Not his state.
Santorum (6%) - Does a little better than Bachmann last time. Not the sole social conservative this time.
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2012 NH Caucus: 39% Romney, 23% Paul, 17% Huntsman, 9% Gingrich, 9% Santorum, 1% Perry.
Again let's assume the camps in 2016 are: Moderates (Bush and Christie), Libertarians (Paul), Social Conservatives (Huckabee and Santorum), and The Base (Cruz, Walker, and Perry). More votes for moderates and less for social conservatives.
Paul (23%) - Libertarian NH.
Christie (21%) - Northeast home advantage.
Bush (18%) - Money and establishment support.
Walker (12%) - Ends up in 4th again.
Cruz (10%) - Too extreme for NH.
Huckabee (8%) - The social conservative camp is small in NH.
Perry (5%) - Did pretty terrible last time.
Santorum (3%) - Splits the small social conservative vote.
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Paul - Gets a boost out of these first two states. Not the frontrunner because he lacks establishment backing and money but definitely in the running. Can he expand beyond the libertarian camp to pull support from "the base"?
Bush and Christie - They're playing the long game. I think Christie is more likely to "pull a Giuliani" though by bombing in SC and NC.
Huckabee - The social conservative niche candidate...Santorum drops out.
Cruz - Hoping to catch fire in the south and coalesce support from "the base" and the social conservatives.
Perry - Does just well enough to pin his hopes on the south.
Walker - Does just well enough to pin his hopes on the midwest.
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The next three are Nevada, South Carolina, and North Carolina.
Paul - Does well in NV and so-so in SC and NC?
Bush and Christie - Bush does OK in all three...Christie bombs in the south. Bush replaces Christie as the establishment choice.
Huckabee - Not so great in NV but OK in SC and NC.
Cruz - Has decent showings in all three.
Perry - So-so in SC and NC...drops.
Walker - OK in NV but pretty bad showings in SC and NC...sticks around for some midwest states.
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Revised thoughts...
Bush - The frontrunner but narrowly.
Christie - Needs a win or at least a close 2nd in NH to avoid being another Huntsman. Can't have totally embarrassing showings in the south.
Paul and Cruz - I think both have a good shot at surviving the first states no matter what. I think Paul has as good a shot as anyone at winning IA and NH. Cruz needs a solid showing in Iowa and NV, SC, NC.
Walker, Perry, and Huckabee - Hoping to breakout in the midwest/south? Which states do these guys hope to win or at least finish 2nd among the first five? Walker: IA? Huckabee: IA, SC, NC? Perry: SC and NC. Would that be enough for them to survive?
Santorum and Carson - No chance.