Two new pieces of data today as we continue to adjust the trims on our Who Will Be the Nominee© model, neither of which I think has particular importance in shaping the ultimate answer, but both of which I think are worthy launching points for tangential discussions. First, Chris Christie has announced he’s out. Second, Herman Cain is leading the field in three new state-level polls.

I would suggest, echoing Jonathan Bernstein, that Christie’s decision was probably made more out of strategic hopelessness than out of any sort of conviction or intuition. There’s really not a great space for him to enter this field, unless his plan was to remain a Rorschach test for the hopes and dreams of conservatives across the spectrum. Which is, of course, impossible once you actually start campaigning for President. And despite the longings of the lonely northeast conservatives, this just ain’t your grandfather’s GOP, and (with apologies to Celtics fans) Thomas Dewey and Nelson Rockefeller are not walking through that door. Nor would they win the nomination if they did. And even if Christie were to run, his plan almost certainly would not have been to join Huntsman in trying to outflank Romney to the left; his path to victory, however vague, would have been to take his turn in Perry’s shoes, trying to unseat Romney from the right, I think.

With Christie out of the way and Perry seemingly falling out of invisible-primary favor, I think we are at a point in which a non-announced candidate could step into the race and make a reasonable, immediate impact. If Palin decides to run, this strikes me as the moment. Ditto Giuliani. Not that I think either of them stand much chance, or that either of them is going to run. But there is a media vacuum, of sorts, and that is plausible important, I suppose.

And this brings me to Cain. Yes, three polls conducted by one firm on one day are not worth, as they say, a warm bucket of piss. But I’m also completely not surprised that this sort of unstable opinion fluctuation is occurring. That it happened to Cain? I guess that’s a bit surprising. But that it is happening in general? Not at all. Primaries — especially large field primaries — are to a certain degree coordination games. Many of the candidates are ideologically similar and most agree with each other on the fundamental party issues. So voter opinion is fluid and shifts in opinion are hardly the stuff of iron-willed conviction. Heck, most candidate “surges” probably just reflect media attention on the newest flavor of the week, which may or may not reflect underlying reality. So any trends that happen prior to, you know, the actual primaries is likely to include a lot of fluidity if candidates don’t live up to the personality or other expectations of the half-paying-attention chattering class on any given day or week. But when the actual voting starts, we could very easily be looking at Romney vs. Perry. In fact, it’s still the odds-on favorite.

But even if the opinion polls accurately reflect the true state of the world (and not just weekly coverage variation and semi-random trends from loosely-committed voters), it’s still not surprising. Whether driven by first-person or media-filtered observation, it doesn’t seem at all unusual to me that an opinion poll is showing odd movement regarding candidate support. Non-Romney primary voters and opinion leaders are continually seeking a candidate who can defeat him; they can coordinate on different individuals until one sticks, without any penalty and without giving up their right to return to a previously-tried candidate. In fact, putting every non-Romney candidate front and center is the best way to try and bring him down; it’s not even necessary that the candidate who does the most damage become the nominee. It’s almost Darwinian: they tried Bachmann, they tried Perry, and now they are trying Cain. Soon enough they will probably be back to Perry. (Of course, if Cain continues to gain popularity, it will require a massive re-evaluation of racial theories of GOP hostility toward Obama.)

I use the word “try” loosely. It’s not like anyone is pulling the strings here on a puppet. The aggregation for such things is more natural (and thus harder to control) than any oligarchic intent, although I do think that money and opinion leaders can strongly shape it. But this leads to my final point: imagine you are the political party, or at least that you have total dictatorial control over the party. If your goal is to maximize the utility of holding the Presidency in 2013, then your basic calculation is simple: evaluate each candidate by multiplying their estimated probability of winning the office times their estimated utility as President. Off the cuff, of course, Romney scores high on the probability of winning, but probably only mediocre on utility, for a conservative party.

Cain, on the other hand, doesn’t score particularly high on either count. His probability of winning is probably somewhat lower than the other candidates, simply because he’s an inexperienced politician. And for the same reason, his utility in office is probably low. He may not have the first clue how to wield political power. But that’s not his biggest downside, from the point of view of a party in 2012. His real problem is that the variance on the estimated probability and utility is massive. His unknown qualities, which might be appealing in some contexts, are horrifying to a party in this context. The 2012 election is a rare situation in which an incumbent president might not be a favorite to win the office. That strikes me as the exact situation in which an opposition party has no interest in nominating anything but a safe candidate of known quantity, who may not have the highest potential utility, but has little danger of imploding during the general election and blowing the opportunity.

I will continue to believe this as long as Cain is popular. If the powers-that-be in the GOP have as much influence over the candidate field as I think they do (which is, to say, a decent amount), Cain cannot possibly be the nominee. Party leaders know this by strategy. The chattering class knows this by calculation. And I think the average voter knows this, by intuition. Untested candidates with little political experience might be plausibly party selections in seemingly hopeless situations. But in this case, my money is still on the GOP to select Romney, save a safe conservative arising from the ashes or Rick Perry proving himself as such.