Conventional wisdom seems to be rapidly cementing around the idea that former Massachusetts governor Mitt Romney is something close to the can’t miss Republican presidential nominee.

MUSCATINE, IA - DECEMBER 28: Republican presidential candidate and former Massachusetts Gov. Mitt Romney participates in a question-and-answer session with members of an overflow crowd at Elly's Tea and Coffee December 28, 2011 in Muscatine, Iowa. (Photo by Chip Somodevilla/Getty Images

His stock is rising — literally — on InTrade, and even his advisers, privately of course, are brimming with confidence about his prospects.

And, any objective look at the current state of play in the race affirms the sentiment that if you are a betting man — and the Fix is not — then Romney is the best bet to be the nominee.

But, politics is unpredictable — it’s why we love it, after all — and there are still a number of potential scenarios by which Romney doesn’t end up as his party’s standard bearer next year.

We lay out a few of the most likely — though, to be clear, none of these is particularly likely at the moment — scenarios below. And make sure to check out Nate Silver’s take on how/why Romney could still come up short too.

* An Iowa disappointment: The Romney campaign has done a very good job of managing Iowa expectations — until the last week or so. Romney and his affiliated super PAC — “Restore Our Future” — are spending millions of dollars on TV ads in the state. Romney surrogates are spreading out all over Iowa to make the case for him. And the candidate himself is in the midst of a three-day bus tour to rally support in the Hawkeye State.

Given that level of spending and activity, it’s impossible for the Romney team to argue that Iowa doesn’t matter to their electoral calculus. Iowa may not be a must-win for Romney but he also probably can’t afford to come in behind anyone other than Texas Rep. Ron Paul next Tuesday night. If he does, his currently steady lead in New Hampshire could erode quickly.

And, if Romney does lose to Paul, the margin of that defeat could matter too. A larger than expected gap between the two could well (re)spark the “conservatives just won’t vote for Romney” storyline that is a terrible way for him to spend the week between Iowa and New Hampshire.

* A Huntsman ambush: With all the focus on Iowa, it’s easy to forget that the New Hampshire primary is now just 13 days away.

Former Utah governor Jon Huntsman — and his affiliated super PAC — have been spending millions of dollars on television in the Granite State, mostly on positive ads touting him as an electable conservative.

Couple that spending with a Paul victory in Iowa and a window might be created for a(nother) Romney alternative in the six days that separate the two votes.

Huntsman’s problems — a moderate at least in tone, service in the Obama Administration — remain but he has one thing that no one other than Romney and maybe Texas Gov. Rick Perry possess: the money to run an all-out ad blitz in the runup to New Hampshire.

And because of Huntsman’s positioning — more toward the ideological middle of the party — he must attack Romney in order to rise. Huntsman has yet to catch the sort of New Hampshire magic that propelled Arizona Sen. John McCain to victories in the state in 2000 and 2008. But, it’s possible that the New Hampshire vote breaks late. And no one has spent more time than Huntsman courting it.

A loss — or even a more narrow than expected win — for Romney in New Hampshire could puncture the inevitability balloon surrounding him and force the party or at least some in the party to start looking around, again.

* South Carolina stumble:Four years ago, Romney put together a top-shelf South Carolina consulting team and traveled to the state relentlessly.

But, as the South Carolina primary approached, it became clear that Romney simply wasn’t catching on. He wound up all-but-skipping the Palmetto State to focus time on the Florida primary. (Romney finished fourth in South Carolina.)

This time around Romney has spent far less time and money in South Carolina perhaps under the assumption that it is a state driven more by momentum than anything else.

But, if Romney loses Iowa to Paul and claims an expected victory in New Hampshire, there may not be much momentum for him heading to South Carolina. Add to that the fact that Romney has struggled to win over social conservatives — in 2008 and this race — and that evangelicals are a dominant bloc of voters in South Carolina and it’s tough to see how Romney winds up on top.

His goal will almost assuredly be to minimize South Carolina’s results. But remember that since the Palmetto State moved its primary up to the front of the presidential nominating calendar, the state has always voted for the eventual nominee. (If you forget that point, you will hear it roughly one billion times between now and Jan. 21.) And both Gingrich and Perry are both pointing to South Carolina as their moment — and are likely to stay in the race at least until the state votes.

* Mitt-plosion: In campaigns, stuff happens. Candidates make mistakes — especially when the pressure is on as it will be over the next month or so.

Romney, to his immense credit, has been remarkably on message for almost the entirety of this race. (Notable exception: $10,000 bet). Still, there is always the possibility that Romney says or does something between now and the end of January that raises fundamental questions about his readiness for office.

That seems very unlikely given his track record in the race but if the 2008 campaign taught us anything, it’s to never say never — with apologies to Justin Bieber.