The defining characteristic of the 2012 Republican presidential primary electorate to date has been a fickleness.

FILE - In this June 13, 2011 file photo, Republican presidential candidate, former House Speaker Newt Gingrich and former Massachusetts Gov. Mitt Romney participate in a presidential debate at St. Anselm College in Manchester, N.H. (AP Photo/Jim Cole, File)

Minnesota Rep. Michele Bachmann boomed from June through August 13 when she won the Ames Straw Poll. That was both Bachmann’s best day and worst day — “City Slickers” reference! — as a candidate since Texas Gov. Rick Perry entered the race the same day and effectively stole all of Bachmann’s momentum.

Perry’s boom lasted about two months — from mid August to mid-October — and was busted on the shoals of his rocky debate performances. (If you need a specific date for when Perry officially went bust, try Nov. 9 in Michigan.)

As Perry fell, Cain, perhaps the most unlikely of the conservative alternatives, rose on the strength of his debate performances, his outsider credentials and, of course, his “9-9-9” economic plan.

But even as Cain boomed, the seeds of his bust were apparent. A late October Politico story reported that Cain had been charged with sexual harassment by two women during the 1990s — and it all snowballed from there, leading to his decision to “reassess” his presidential candidacy.

Enter former House Speaker Newt Gingrich whose boom has dovetailed nicely with Cain’s bust.

The question for Gingrich is whether the fickle Republican electorate has, finally, settled on him as the preferred Romney alternative or whether his time in that coveted slot is already beginning to run out.

One thing that may help Gingrich that the past pretenders to the anti-Romney crown didn’t benefit from: the Iowa caucuses are only 32(!) days away.

If Gingrich can maintain his current poll/pole position for the next month, it’s a very real possibility that he wins the caucuses — a victory that would affirm his status as the Romney alternative (and perhaps the favorite for the nomination) once and for all.

The next 15 days then will be critical for Gingrich. There are two Iowa debates scheduled — one on Dec. 10, the other on Dec. 15 — and if he can shine in those and not make any other unforced errors (not a small task for Gingrich), he may cure the conservative primary electorate of its fickleness.

Our Friday Line ranking of the eight candidates with some chance of winding up as the Republican presidential nominee is below. The number one ranked candidate is the most likely likely nominee.

Kudos? Critiques? The comments section awaits

To the Line!

8. Herman Cain: Regardless of what Cain says in his “major” announcement tomorrow in Atlanta tomorrow, his time as a serious presidential candidate has passed. The Cain Train has run out of track. Or left the station. Or run out of steam. Pick your bad metaphor but they all say the same thing: It’s a Cainwreck. (Previous ranking: 3)

7. Rick Santorum: The former Pennsylvania senator is essentially the only candidate in this race who hasn’t shown any boom potential in the race. Even former Utah governor Jon Huntsman was thought to be a serious contender at one point and still isn’t being totally counted out. The question for Santorum is, if Gingrich falters, does he pick up the pieces and turn into the chief Romney alternative? He’s essentially the last conservative alternative that hasn’t benefitted from others’ failings. Stranger things have happened in this race. But time is running out. (Previous ranking: 8)

6. Michele Bachmann: Bachmann is moving up because other candidates are imploding — not through any success of her own. Despite a laser-like focus on Iowa, her poll numbers haven’t moved from single digits all month. Some strategists argue that even if current polls suggest otherwise, the caucuses will still come down to retail politics . But even on the ground, Bachmann is stumbling. Just this week she misappropriated a list of home-schoolers and sent out an erroneous supporter list. These mistakes suggest that her organization isn’t functioning in top form even if she’s a constant presence in the state. (Previous ranking: 7)

5. Ron Paul: The Texas congressman stood in a virtual tie for first place with three other candidates in Iowa in a recent Bloomberg News poll, and he continues to look like he will pull significant votes in many of the early states. For Paul, the more contenders there are, the better. At the same time, getting past 15 to 20 percent in any given state is a very tough slog. A win in Iowa, which isn’t so far-fetched, is about all we can see that might change that. And even then, it would be hard to see this as anything other than a symptom of a fractured field. (Previous ranking: 6)

4. Jon Huntsman: Huntsman’s poll numbers are ticking up somewhat in New Hampshire, not surprising given that a super PAC supporting his candidacy has dropped close to $1.5 million on ads in the state. The question for Huntsman is where he fits in a two-man race between Gingrich and former Massachusetts governor Mitt Romney. At the moment, he still looks a lot like a third wheel. (Previous ranking: 5)

3. Rick Perry: How does the Texas governor stay this high on the Line? Because, despite the fact that polling suggests he is dead in the water, he is one of the only candidates with enough money — $15 million in the bank at the end of September — to, theoretically, make a move if the moment is/was right. Perry’s latest ad, which makes fun of his “Oops” moment, is the best commercial he has run in the race so far but it’s probably three weeks too late. Perry is still ideologically the best fit among the top-tier candidates for the mood of the Republican electorate but all indications are that those voters have written him off. (Previous ranking: 2)

2. Newt Gingrich: In an election year filled with absolutely amazing storylines, the re-rise of Gingrich may be the most amazing. Left for dead by the political media — and his senior staff, all of whom quit — at the start of the summer, Gingrich has somehow found his way back to (or close to) the top of the Republican field. Gingrich, as anyone who has spent more than five minutes in political Washington knows, is a man of tremendous abilities and just as tremendous flaws. (His closest Democratic analog? Bill Clinton.) At the moment, Republican primary voters seem willing to overlook Gingrich’s past flip-flops and foibles. Will that attitude last through Jan. 3? (Previous ranking: 4)

1. Mitt Romney: Romney has been the steadiest force in the Republican race. For the better part of the last year, he has been consistently between 20 percent and 25 percent in national primary polls. But, is that a good thing? It’s clear that there are a certain segment of (primarily) conservative voters who will vote for whoever is the most viable alternative to Romney. And yet, he is, without question, the best funded and best organized candidate nationally and in early states. (His decision to begin running TV ads in Iowa suggests his campaign has finally decided he can — and needs to — win in the Hawkeye State.) Romney still is the safest bet to be the Republican nominee but the possibility of a one-on-one race between him and Gingrich as the conservative alternative should scare his campaign team. (Previous ranking: 1)

Aaron Blake and Rachel Weiner contributed to this report