As long as I already have third-party runs on my mind, how about a little pre-debunking of all the what-if fantasies that political reporters are going to run at you over the next year. Let’s see … we already have that a third-party candidate will not win the presidency. I’ll add one that you’ve been hearing for the past few months but has finally faded, which is that no candidate will jump into the nomination contest this late and win it. What else?

There won’t be a deadlocked convention. The GOP field has already been winnowed nicely, and we can count on a winner emerging from the primaries and caucuses, most likely early in the process.

The Republican nominee won’t be destroyed by a lack of enthusiasm within the GOP base. It doesn’t matter how Republicans feel about Mitt Romney now; once he (or someone else) is the nominee, they’ll be hit with months of stories featured in the news sources they trust about what a swell guy and great conservative Mitt Romney has always been.

Barack Obama won’t dump Joe Biden. It is possible that in the abstract some other candidate — Hillary Clinton is the most popular mention, but we’ll see talk of others — would run better. But in reality, dumping a successful vice president would be an admission that something is seriously wrong with the administration, and any potential replacement would entail risks that a sitting vice president doesn’t have. The logic of the situation calls for keeping Biden.

A key moment in the presidential debates next fall won’t decide the contest. Political scientists disagree about how important campaigns are at all (compared to fundamentals such as economic performance), but it’s fairly certain that individual events within general election campaigns are just not that critical. Similarly, secret and enormous new funding sources unleashed by the Supreme Court won’t be the real story in the race for the White House. It’s possible that funding changes could matter at the margins, and Citizens United really might matter a lot at the sub-presidential level, but there are good structural reasons why money just isn’t that important in presidential general elections.

Last one: Despite plausibility on the surface, we’re not going to see a 100 percent flip at the national level, in which Republicans take the White House and the Senate but Democrats win the House. Each of these three changes is perfectly plausible on its own, but they’re not going to happen together. In reality, too many people vote by party for a GOP presidential victory to be matched by a very strong Democratic win in the House.

Except, one more: Politics combines regularities that can be observed and extrapolated from — and human action, which is unpredictable. And so there’s every chance that at least something will happen that really is a break from the past. Which means that every prediction or Iron Law of Politics should have a clear caveat that it’ll only work if people behave as they normally do. Which almost always is the case. Except when it isn’t.